Method and an apparatus for reproducing bitstream having non-sequential system clock data seamlessly therebetween

ABSTRACT

A system stream contiguous reproduction apparatus to which are input one or more system streams interleaving at least moving picture data and audio data, and system stream connection information includes a system clock STC generator for producing the system clock that is used as the system stream reproduction reference clock. The system stream contiguous reproduction apparatus further includes one or more signal processing decoders that operate referenced to the system clock STC, decoder buffers for temporarily storing the system stream data transferred to the corresponding signal processing decoders, and STC selectors for selecting a system clock STC referenced by the signal processing decoders when decoding the first system stream, and another system clock STC referenced by the signal processing decoders when decoding a second system stream reproduced contiguously to the first system stream.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for seamlesslyreproducing a bitstream having non-sequential system clock data thereinand, more specifically, to a bits ream for use in an authoring systemfor variously processing a data bitstream comprising the video data,audio data, and sub-picture data constituting each of plural programtitles containing related video data, audio data, and sub-picture datacontent to generate a bitstream from which a new title containing thecontent desired by the user can be reproduced, and efficiently recordingand reproducing the generated bitstream using a particular recordingmedium.

2. Description of the Prior Art

Authoring systems used to produce program titles comprising relatedvideo data, audio data, and sub-picture data by digitally processing,for example, multimedia data comprising video, audio, and sub-picturedata recorded to laser disk or video CD formats are currently available.Systems using Video-Cds in particular are able to record video data to aCD format disk, which was originally designed with an approximately 600MB recording capacity for storing digital audio data only, by using suchhigh efficiency video compression techniques as MPEG. As a result of theincreased effective recording capacity achieved using data compressiontechniques, karaoke titles and other conventional laser diskapplications are gradually being transferred to the video CD format.

Users today expect both sophisticated title content and highreproduction quality. To meet these expectations, each title must becomposed from bitstreams with an increasingly deep hierarchicalstructure. The data size of multimedia titles written with bitstreamshaving such deep hierarchical structures, however, is ten or more timesgreater than the data size of less complex titles. The need to editsmall image (title) details also makes it necessary to process andcontrol the bitstream using low order hierarchical data units.

It is therefore necessary to develop and prove a bitstream structure andan advanced digital processing method including both recording andreproduction capabilities whereby a large volume, multiple levelhierarchical digital bitstream can be efficiently controlled at eachlevel of the hierarchy. Also needed are an apparatus for executing thisdigital processing method, and a recording media to which the bitstreamdigitally processed by the apparatus can be efficiently recorded forstorage and from which the recorded information can be quicklyreproduced.

Means for increasing the storage capacity of conventional optical diskshave been widely researched to address the recording medium aspect ofthis problem. One way to increase the storage capacity of the opticaldisk is to reduce the spot diameter D of the optical (laser) beam. Ifthe wavelength of the laser beam is 1 and the aperture of the objectivelens is NA, then the spot diameter D is proportional to 1/NA, and thestorage capacity can be efficiently improved by decreasing 1 andincreasing NA.

As described, for example, in U.S. Pat. No. 5,235,581, however, comacaused by a relative tilt between the disk surface and the optical axisof the laser beam (hereafter "tilt") increases when a large aperture(high NA) lens is used. To prevent tilt-induced coma, the transparentsubstrate must be made very thin. The problem is that the mechanicalstrength of the disk is low when the transparent substrate is very thin.

MPEG1, the conventional method of recording and reproducing video,audio, and graphic signal data, has also been replaced by the morerobust MPEG2 method, which can transfer large data volumes at a higherrate. It should be noted that the compression method and data format ofthe MPEG2 standard differ somewhat from those of MPEG1. The specificcontent of and differences between MPEG1 and MPEG2 are described indetail in the ISO-11172 and ISO-13818 MPEG standards, and furtherdescription thereof is omitted below.

Note, however, that while the structure of the encoded video stream isdefined in the MPEG2 specification, the hierarchical structure of thesystem stream and the method of processing lower hierarchical levels arenot defined.

As described above, it is therefore not possible in a conventionalauthoring system to process a large data stream containing sufficientinformation to satisfy many different user requirements. Moreover, evenif such a processing method were available, the processed data recordedthereto cannot be repeatedly used to reduce data redundancy becausethere is no large capacity recording medium currently available that canefficiently record and reproduce high volume bitstreams such asdescribed above.

More specifically, particular significant hardware and softwarerequirements must be satisfied in order to process a bitstream using adata unit smaller than the title. These specific hardware requirementsinclude significantly increasing the storage capacity of the recordingmedium and increasing the speed of digital processing; softwarerequirements include inventing an advanced digital processing methodincluding a sophisticated data structure.

Therefore, the object of the present invention is to provide aneffective authoring system for controlling a multimedia data bitstreamwith advanced hardware and software requirements using a data unitsmaller than the title to better address advanced user requirements.

To share data between plural titles and thereby efficiently utilizeoptical disk capacity, multi-scene control whereby scene data common toplural titles and the desired scenes on the same time-base from withinmulti-scene periods containing plural scenes unique to particularreproduction paths can be freely selected and reproduced is desirable.

However, when plural scenes unique to a reproduction path within themulti-scene period are arranged on the same time-base, the scene datamust be contiguous. Unselected multi-scene data is therefore unavoidablyinserted between the selected common scene data and the selectedmulti-scene data. The problem this creates when reproducing multi-scenedata is that reproduction is interrupted by this unselected scene data.

In other words, except when a video object VOB, which is normally asingle-stream title editing unit, is divided into discrete streams,seamless reproduction cannot be achieved by simply connecting andreproducing individual VOBs. This is because while the reproduction ofvideo, audio, and sub-picture streams forming each VOB must besynchronized, the means for achieving this synchronization is enclosedin each VOB. As a result, the synchronization means will not functionnormally at VOB connections if the VOBs are simply connected together.

The object of the present invention is therefore to provide areproduction apparatus enabling seamless reproduction whereby scene datacan be reproduced without intermittence even from these multi-sceneperiods.

The object of the present invention is therefore to provide an opticaldisk medium from which data can be seamlessly reproduced without audioor video intermitting even in such multi-scene periods, and areproducing apparatus implementing the recording and reproducing method.

The present application is based upon Japanese Patent Application No.7-276710 and 8-041583, which were filed on Sep. 29, 1995 and Feb. 28,1996, respectively, the entire contents of which are expresslyincorporated by reference herein.

SUMMARY OF THE INVENTION

The present invention has been developed with a view to substantiallysolving the above described disadvantages and has for its essentialobject to provide an improved method and apparatus for reproducing abitstream having non-sequential system clock data seamlesslytherebetween.

In order to achieve the aforementioned objective, a system streamcontiguous reproduction apparatus to which are input one or more systemstreams interleaving at least moving picture data and audio data, andsystem stream connection information comprises a system clock STCgenerator for producing the system clock that is used as the systemstream reproduction reference clock, one or more signal processingdecoders that operate referenced to the system clock STC, decoderbuffers for temporarily storing the system stream data transferred tothe corresponding signal processing decoders, and STC selectors forselecting a system clock STC referenced by the signal processingdecoders when decoding the first system stream, and another system clockSTC referenced by the signal processing decoders when decoding a secondsystem stream reproduced contiguously to the first system stream.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clear from the following description taken in conjunction withthe preferred embodiments thereof with reference to the accompanyingdrawings throughout which like parts are designated by like referencenumerals, and in which:

FIG. 1 is a graph schematically showing a structure of a multimedia bitstream according to the present invention,

FIG. 2 is a block diagram showing an authoring encoder according to thepresent invention,

FIG. 3 is a block diagram showing an authoring decoder according to thepresent invention,

FIG. 4 is a side view of an optical disk storing the multi media bitstream of FIG. 1,

FIG. 5 is an enlarged view showing a portion confined by a circle ofFIG. 4,

FIG. 6 is an enlarged view showing a portion confined by a circle ofFIG. 5,

FIG. 7 is a side view showing a variation of the optical disk of FIG. 4,

FIG. 8 is a side view showing another variation of the optical disk ofFIG. 4,

FIG. 9 is a plan view showing one example of track path formed on therecording surface of the optical disk of FIG. 4,

FIG. 10 is a plan view showing another example of track path formed onthe recording surface of the optical disk of FIG. 4,

FIG. 11 is a diagonal view schematically showing one example of a trackpath pattern formed on the optical disk of FIG. 7,

FIG. 12 is a plan view showing another example of track path formed onthe recording surface of the optical disk of FIG. 7,

FIG. 13 is a diagonal view schematically showing one example of a trackpath pattern formed on the optical disk of FIG. 8,

FIG. 14 is a plan view showing another example of track path formed onthe recording surface of the optical disk of FIG. 8,

FIG. 15 is a graph in assistance of explaining a concept of parentalcontrol according to the present invention,

FIG. 16 is a graph schematically showing the structure of a multimediabit stream for use in Digital Video Disk system according to the presentinvention,

FIG. 17 is a graph schematically showing the encoded video streamaccording to the present invention,

FIG. 18 is a graph schematically showing an internal structure of avideo zone of FIG. 16.

FIG. 19 is a graph schematically showing the stream managementinformation according to the present invention,

FIG. 20 is a graph schematically showing the structure the navigationpack NV of FIG. 17,

FIG. 21 is a graph is assistance of explaining a concept of parentallock playback control according to the present invention,

FIG. 22 is a graph schematically showing the data structure used in adigital video disk system according to the present invention,

FIG. 23 is a graph in assistance of explaining a concept of Multi-anglescene control according to the present invention,

FIG. 24 is a graph in assistance of explaining a concept of multi scenedata connection,

FIG. 25 is a block diagram showing a DVD encoder according to thepresent invention,

FIG. 26 is a block diagram showing a DVD decoder according to thepresent invention,

FIG. 27 is a graph schematically showing an encoding information tablegenerated by the encoding system controller of FIG. 25,

FIG. 28 is a graph schematically showing an encoding information table,

FIG. 29 is a graph schematically showing an encoding parameters used bythe video encoder of FIG. 25,

FIG. 30 is a graph schematically showing an example of the contents ofthe program chain information according to the present invention,

FIG. 31 is a graph schematically showing another example of the contentsof the program chain information according to the present invention,

FIG. 32 is a block diagram showing a synchronizer of FIG. 26 accordingto the present invention,

FIG. 33 is a graph in assistance of explaining a concept of multi-anglescene control according to the present in invention,

FIG. 34 is a flow chart, formed by FIGS. 34A and 34B, showing anoperation of the DVD encoder of FIG. 25,

FIG. 35 is a flow chart showing details of the encode parameterproduction-sub-routine of FIG. 34,

FIG. 36 is a flow chart showing the details of the VOB data settingroutine of FIG. 35,

FIG. 37 is a flow chart showing the encode parameters generatingoperation for a seamless switching,

FIG. 38 is a flow chart showing the encode parameters generatingoperation for a system stream,

FIG. 39 is a block diagram showing the STC generator of FIG. 32,

FIG. 40 is a graph in assistance of explaining the relationship therelationship between the SCR, APTS, VDTS, and VPTS values,

FIG. 41 is a block diagram showing a modification of the synchronizer ofFIG. 32,

FIG. 42 is a block diagram showing a synchronization controller of FIG.41,

FIG. 43 is a flow chart showing an operation of the syncronizationcontroller of FIG. 42,

FIG. 44 is a graph in assistance of explaining the relationship betweenthe system clock reference SCR, the audio playback starting timeinformation APTS, the decoder reference clock STC, and the videoplayback starting time VPTS,

FIG. 45 is a graph in assistance of explaining the relationship betweenthe recording positions and values of SCR, APTS, and VPTS when VOB #1and VOB #2 are seamlessly reproduced,

FIG. 46 is a graph in assitance of explaining the relationship betweenthe SCR, APTS, and VPTS values and recording positions in each VOB,

FIG. 47 is a graph in assistance of explaining the relationship betweenthe SCR, APTS, and VPTS values and recording positions in the VOB,

FIG. 48 is a graph showing a time line from input of the VOB in FIG. 47to the system decoder to output of the last audio and video reproductiondata,

FIG. 49 is a flow chart showing the operation of the DVD encoder of FIG.26,

FIG. 50 is a flow chart showing details of the multi-angle non-seamlessswitching control routine of FIG. 49,

FIG. 51 is a flow chart showing details of the multi-angle seamlessswitching control routine of FIG. 49,

FIG. 52 is a flow chart showing details of the parental lock sub-routineof FIG. 49,

FIG. 53 is a flow chart showing details of the single scene subroutineof FIG. 49,

FIGS. 54 and 55 are graphs showing decoding information table producedby the decoding system controller of FIG. 26,

FIG. 56 is a flow chart showing the operation of the DVD decoder DCD ofFIG. 26,

FIG. 57 is a low chart showing details of reproduction extracted PGCrouting of FIG. 56,

FIG. 58 is a flow chart showing details of decoding data process of FIG.57, performed by the stream buffer,

FIG. 59 is a flow chart showing details of the decoder synchronizationprocess of FIG. 58,

FIG. 60 is a flow chart showing an operation of the STC selectioncontroller of FIG. 39 during a non-seamless reproduction operation,

FIG. 61 is a flow chart showing the operation of the STC selectioncontroller of FIG. 39 during a seamless reproduction operation,

FIG. 62 is a flow chart showing the data transferring operation of FIG.57,

FIG. 63 is a flow chart showing details of the non multi-angle decodingprocess of FIG. 62,

FIG. 64 is a flow chart showing details of the non-multi-angledinterleave process of FIG. 63,

FIG. 65 is a flow chart showing details of the non-multi-angledcontiguous block process of FIG. 63,

FIG. 66 is a flow chart showing a modification of FIG. 63,

FIG. 67 is a flow chart showing details of the seamless multi-angledecoding process of FIG. 62,

FIG. 68 is a flow chart showing details of non-seamless multi-angledecoding process of FIG. 62,

FIG. 69 is a block diagram showing details of the stream buffer of FIG.26,

FIG. 70 is a flow chart showing the encode parameters generatingoperation for a system stream containing a single scene,

FIG. 71 is a graph schematically showing an actual arrangement of datablocks recorded to a data recording track on a recording mediumaccording to the present invention;

FIG. 72 is a graph schematically showing contiguous block regions andinterleaved block regions array,

FIG. 73 is a graph schematically showing a content of a VTS title VOBSaccording to the present invention, and

FIG. 74 is a graph schematically showing an internal data structure ofthe interleaved block regions according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Data Structure of theAuthoring System

The logic structure of the multimedia data bitstream processed using therecording apparatus, recording medium, reproduction apparatus, andauthoring system according to the present invention is described firstbelow with reference to FIG. 1.

In this structure, one title refers to the combination of video andaudio data expressing program content recognized by a user foreducation, entertainment, or other purpose. Referenced to a motionpicture (movie), one title may correspond to the content of an entiremovie, or to just one scene within said movie.

A video title set (VTS) comprises the bitstream data containing theinformation for a specific number of titles. More specifically, each VTScomprises the video, audio, and other reproduction data representing thecontent of each title in the seq, and control data for controlling thecontent data.

The video zone VZ is the video data unit processed by the authoringsystem, and comprises a specific number of video title sets. Morespecifically, each video zone is a linear sequence of K+1 video titlesets numbered VTS #0-VTS #K where K is an integer value of zero orgreater. One video title set, preferably the first video title set VTS#0, is used as the video manager describing the content information ofthe titles contained in each video title set.

The multimedia bitstream MBS is the largest control unit of themultimedia data bitstream handled by the authoring system of the presentinvention, and comprises plural video zones VZ.

Authoring Encoder EC

A preferred embodiment of the authoring encoder EC according to thepresent invention for generating a new multimedia bitstream MES byre-encoding the original multimedia bitstream MES according to thescenario desired by the user is shown in FIG. 2. Note that the originalmultimedia bitstream MES comprises a video stream St1 containing thevideo information, a sub-picture stream St3 containing caption text andother auxiliary video information, and the audio stream St5 containingthe audio information.

The video and audio streams are the bitstreams containing the video andaudio information obtained from the source within a particular period oftime. The sub-picture stream is a bitstream containing momentary videoinformation relevant to a particular scene. The sub-picture data encodedto a single scene may be captured to video memory and displayedcontinuously from the video memory for plural scenes as may benecessary.

When this multimedia source data St1, St3, and St5 is obtained from alive broadcast, the video and audio signals are supplied in real-timefrom a video camera or other imaging source; when the multimedia sourcedata is reproduced from a video tape or other recording medium, theaudio and video signals are not real-time signals.

While the multimedia source stream is shown in FIG. 2 as comprisingthese three source signals, this is for convenience only, and it shouldbe noted that the multimedia source stream may contain more than threetypes of source signals, and may contain source data for differenttitles. Multimedia source data with audio, video, and sub-picture datafor plural titles are referred to below as multi-title streams.

As shown in FIG. 2, the authoring encoder EC comprises a scenario editor100, encoding system controller 200, video encoder 300, video streambuffer 400, sub-picture encoder 500, sub-picture stream buffer 600,audio encoder 700, audio stream buffer 800, system encoder 900, videozone formatter 1300, recorder 1200, and recording medium M.

The video zone formatter 1300 comprises video object (VOB) buffer 1000,formatter 1100, and volume and file structure formatter 1400.

The bitstream encoded by the authoring encoder EC of the presentembodiment is recorded, by way of example only, to an optical disk.

The scenario editor 100 of the authoring encoder EC outputs the scenariodata, i.e., the user-defined editing of instructions. The scenario datacontrols editing the corresponding parts of the multimedia bitstream MBSaccording to the user's manipulation of the video, sub-picture, andaudio components of the original multimedia title. This scenario editor100 preferably comprises a display, speaker(s), keyboard, CPU, andsource stream buffer. The scenario editor 100 is connected to anexternal multimedia bitstream source from which the multimedia sourcedata St1, St3, and St5 are supplied.

The user is thus able to reproduce the video and audio components of themultimedia source data using the display and speaker to confirm thecontent of the generated title. The user is then able to edit the titlecontent according to the desired scenario using the keyboard, mouse, andother command input devices while confirming the content of the title onthe display and speakers. The result of this multimedia datamanipulation is the scenario data St7.

The scenario data St7 is basically a set of instructions describing whatsource data is selected from all or a subset of the source datacontaining plural titles within a defined time period, and how theselected source data is reassembled to reproduce the scenario (sequence)intended by the user. Based on the instructions received through thekeyboard or other control device, the CPU codes the position, length,and the relative time-based positions of the edited parts ofthe-respective multimedia source data streams St1, St3, and St5 togenerate the scenario data St7.

The source stream buffer has a specific capacity, and is used to delaythe multimedia source data streams St1, St3, and St5 a known time Td andthen output streams St1, St3, and St5.

This delay is required for synchronization with the editor encodingprocess. More specifically, when data encoding and user generation ofscenario data St7 are executed simultaneously, i.e., when encodingimmediately follows editing, time Td is required to determine thecontent of the multimedia source data editing process based on thescenario data St7 as will be described further below. As a result, themultimedia source data must be delayed by time Td to synchronize theediting process during the actual encoding operation. Because this delaytime Td is limited to the time required to synchronize the operation ofthe various system components in the case of sequential editing asdescribed above, the source stream buffer is normally achieved by meansof a high speed storage medium such as semiconductor memory.

During batch editing in which all multimedia source data is encoded atonce ("batch encoded") after scenario data St7 is generated for thecomplete title, delay time Td must be long enough to process thecomplete title or longer. In this case, the source stream buffer may bea low speed, high capacity storage medium such as video tape, magneticdisk, or optical disk.

The structure (type) of media used for the source stream buffer maytherefore be determined according to the delay time Td required and theallowable manufacturing cost.

The encoding system controller 200 is connected to the scenario editor100 and receives the scenario data St7 therefrom. Based con thetime-base position and length information of the edit segment containedin the scenario data St7, the encoding system controller 200 generatesthe encoding parameter signals St9, St11, and St13 for encoding the editsegment of the multimedia source data. The encoding signals St9, St11,and St13 supply the parameters used for video, sub-picture, and audioencoding, including the encoding start and end timing. Note thatmultimedia source data St1, St3, and St5 are output after delay time Tdby the source stream buffer, and are therefore synchronized to encodingparameter signals St9, St11, and St13.

More specifically, encoding parameter signal St9 is the video encodingsignal specifying the encoding timing of video stream St1 to extract theencoding segment from the video stream St1 and generate the videoencoding unit. Encoding parameter signal St11 is likewise thesub-picture stream encoding signal used to generate the sub-pictureencoding unit by specifying the encoding timing for sub-picture streamSt3. Encoding parameter signal St13 is the audio encoding signal used togenerate the audio encoding unit by specifying the encoding timing foraudio stream St5.

Based on the time-base relationship between the encoding segments ofstreams St1, St3, and St5 in the multimedia source data contained inscenario data St7, the encoding system controller 200 generates thetiming signals St21, St23, and St25 arranging the encodedmultimedia-encoded stream in the specified time-base relationship.

The encoding system controller 200 also generates the reproduction timeinformation IT defining the reproduction time of the title editing unit(video object, VOB), and the stream encoding data St33 defining thesystem encode parameters for multiplexing the encoded multimedia streamcontaining video, audio, and sub-picture data. Note that thereproduction time information IT and stream encoding data St33 aregenerated for the video object VOB of each title in one video zone VZ.

The encoding system controller 200 also generates the title sequencecontrol signal St39, which declares the formatting parameters forformatting the title editing units VOB of each of the streams in aparticular time-base relationship as a multimedia bitstream. Morespecifically, the title sequence control signal St39 is used to controlthe connections between the title editing units (VOB) of each title inthe multimedia bitstream MBS, or to control the sequence of theinterleaved title editing unit (VOBs) interleaving the title editingunits VOB of plural reproduction paths.

The video encoder 300 is connected to the source stream buffer of thescenario editor 100 and to the encoding system controller 200, andreceives therefrom the video stream St1 and video encoding parametersignal St9, respectively. Encoding parameters supplied by the videoencoding signal St9 include the encoding start and end timing, bit rate,the encoding conditions for the encoding start and end, and the materialtype. Possible material types include NTSC or PAL video signal, andtelecine converted material. Based on the video encoding parametersignal St9, the video encoder 300 encodes a specific part of the videostream St1 to generate the encoded video stream St15.

The sub-picture encoder 500 is similarly connected to the source streambuffer of the scenario editor 100 and to the encoding system controller200, and receives therefrom the sub-picture stream St3 and sub-pictureencoding parameter signal St11, respectively. Based on the sub-pictureencoding parameter signal St11, the sub-picture encoder 500 encodes aspecific part of the sub-picture stream St3 to generate the encodedsub-picture stream St17.

The audio encoder 700 is also connected to the source stream buffer ofthe scenario editor 100 and to the encoding system controller 200, andreceives therefrom the audio stream St5 and audio encoding parametersignal St13, which supplies the encoding start and end timing. Based onthe audio encoding parameter signal St13, the audio encoder 700 encodesa specific part of the audio stream St5 to generate the encoded audiostream St19.

The video stream-buffer 400 is connected to the video encoder 300 and tothe encoding system controller 200. The video stream buffer 400 storesthe encoded video stream St15 input from the video encoder 300, andoutputs the stored encoded video stream St15 as the time-delayed encodedvideo stream St27 based on the timing signal St21 supplied from theencoding system controller 200.

The sub-picture stream buffer 600 is similarly connected to thesub-picture encoder 500 and to the encoding system controller 200. Thesub-picture stream buffer 600 stores the encoded sub-picture stream St17output from the sub-picture encoder 500, and then outputs the storedencoded sub-picture stream St17 as time-delayed encoded sub-picturestream St29 based on the timing signal St23 supplied from the encodingsystem controller 200.

The audio stream buffer 800 is similarly connected to the audio encoder700 and to the encoding system controller 200. The audio stream buffer800 stores the encoded audio stream St19 input from the audio encoder700, and then outputs the encoded audio stream St19 as the time-delayedencoded audio stream St31 based on the timing signal St25 supplied fromthe encoding system controller 200.

The system encoder 900 is connected to the video stream buffer 400,sub-picture stream buffer 600, audio stream buffer 800, and the encodingsystem controller 200, and is respectively supplied thereby with thetime-delayed encoded video stream St27, time-delayed encoded sub-picturestream St29, time-delayed encoded audio stream St31, and the streamencoding data St33. Note that the system encoder 900 is a multiplexerthat multiplexes the time-delayed streams St27, St29, and St31 based onthe stream encoding data St33 (timing signal) to generate title editingunit (VOB) St35. The stream encoding data St33 contains the systemencoding parameters, including the encoding start and end timing.

The video zone formatter 1300 is connected to the system encoder 900 andthe encoding system controller 200 from which the title editing unit(VOB) St35 and title sequence control signal St39 (timing signal) arerespectively supplied. The title sequence control signal St39 containsthe formatting start and end timing, and the formatting parameters usedto generate (format) a multimedia bitstream MBS. The video zoneformatter 1300 rearranges the title editing units (VOB) St35 in onevideo zone VZ in the scenario sequence defined by the user based on thetitle sequence control signal St39 to generate the edited multimediastream data St43.

The multimedia bitstream MBS St43 edited according to the user-definedscenario is then sent to the recorder 1200. The recorder 1200 processesthe edited multimedia stream data St43 to the data stream St45 format ofthe recording medium M, and thus records the formatted data stream St45to the recording medium M. Note that the multimedia bitstream MBSrecorded to the recording medium M contains the volume file structureVFS, which includes the physical address of the data on the recordingmedium generated by the video zone formatter 1300.

Note that the encoded multimedia bitstream MBS St35 may be outputdirectly to the decoder to immediately reproduce the edited titlecontent. It will be obvious that the output multimedia bitstream MBSwill not in this case contain the volume file structure VFS.

Authoring Decoder

A preferred embodiment of the authoring decoder DC used to decode themultimedia bitstream MBS edited by the authoring encoder EC of thepresent invention, and thereby reproduce the content of each title unitaccording to the user-defined scenario, is described next below withreference to FIG. 3. Note that in the preferred embodiment describedbelow the multimedia bitstream St45 encoded by the authoring encoder ECis recorded to the recording medium M.

As shown in FIG. 3, the authoring decoder DC comprises a multimediabitstream producer 2000, scenario selector 2100, decodinc- systemcontroller 2300, stream buffer 2400, system decoder 2500, video buffer2600, sub-picture buffer 2700, audio buffer 2800, synchronizer 2900,video decoder 3800, sub-picture decoder 3100, audio decoder 3200,synthesizer 3500, video data output terminal 3600, and audio data outputterminal 3700.

The bitstream producer 2000 comprises a recording media drive unit 2004for driving the recording medium M; a reading head 2006 for reading theinformation recorded to the recording medium M and producing the binaryread signal St57; a signal processor 2008 for variously processing theread signal St57 to generate the reproduced bitstream St61; and areproduction controller 2002.

The reproduction controller 2002 is connected to the decoding systemcontroller 2300 from which the multimedia bitstream reproduction controlsignal St53 is supplied, and in turn generates the reproduction controlsignals St55 and St59 respectively controlling the recording media driveunit (motor) 2004 and signal processor 2008.

So that the user-defined video, sub-picture, and audio portions of themultimedia title edited by the authoring encoder EC are reproduced, theauthoring decoder DC comprises a scenario selector 2100 for selectingand reproducing the corresponding scenes (titles). The scenario selector2100 then outputs the selected titles as scenario data to the authoringdecoder DC.

The scenario selector 2100 preferably comprises a keyboard, CPU, andmonitor. Using the keyboard, the user then inputs the desired scenariobased on the content of the scenario input by the authoring encoder EC.Based on the keyboard input, the CPU generates the scenario selectiondata St51 specifying the selected scenario. The scenario selector 2100is connected by an infrared communications device, for example, to thedecoding system controller 2300, to which it inputs the scenarioselection data St51.

Based on the scenario selection data St51, the decoding systemcontroller 2300 then generates the bitstream reproduction control signalSt53 controlling the operation of the bitstream producer 2000.

The stream buffer 2400 has a specific buffer capacity used totemporarily store the reproduced bitstream St61 input from the bitstreamproducer 2000, extract the address information and initialsynchronization data SCR (system clock reference) for each stream, andgenerate bitstream control data St63. The stream buffer 2400 is alsoconnected to the decoding system controller 2300, to which it suppliesthe generated bitstream control data St63.

The synchronizer 2900 is connected to the decoding system controller2300 from which it receives the system clock reference SCR contained inthe synchronization control data St81 to set the internal system clockSTC and supply the reset system clock St79 to the decoding systemcontroller 2300.

Based on this system clock St79, the decoding system controller 2300also generates the stream read signal St65 at a specific interval andoutputs the read signal St65 to the stream buffer 2400.

Based on the supplied read signal St65, the stream buffer 2400 outputsthe reproduced bitstream St61 at a specific interval to the systemdecoder 2500 as bitstream St67.

Based on the scenario selection data St51, the decoding systemcontroller 2300 generates the decoding signal St69 defining the streamIds for the video, sub-picture, and audio bitstreams corresponding tothe selected scenario, and outputs to the system decoder 2500.

Based on the instructions contained in the decoding signal St69,the-system decoder 2500 respectively outputs the video, sub-picture, andaudio bitstreams input from the stream buffer 2400 to the video buffer2600, sub-picture buffer 2700, and audio buffer 2800 as the encodedvideo stream St71, encoded sub-picture stream St73, and encoded audiostream St75.

The system decoder 2500 detects the presentation time stamp PTS anddecoding time stamp DTS of the smallest control unit in each bitstreamSt67 to generate the time information signal St77. This time informationsignal St77 is supplied to the synchronizer 2900 through the decodingsystem controller 2300 as the synchronization control data St81.

Based on this synchronization control data St81, the synchronizer 2900determines the decoding start timing whereby each of the bitstreams willbe arranged in the correct sequence after decoding, and then generatesand inputs the video stream decoding start signal St89 to the videodecoder 3800 based on this decoding timing. The synchronizer 2900 alsogenerates and supplies the sub-picture decoding start signal St91 andaudio stream decoding start signal St93 to the sub-picture decoder 3100and audio decoder 3200, respectively.

The video decoder 3800 generates the video output request signal St84based on the video stream decoding start signal St89, and outputs to thevideo buffer 2600. In response to the video output request signal St84,the video buffer 2600 outputs the video stream St83 to the video decoder3800. The video decoder 3800 thus detects the presentation timeinformation contained in the video stream St83, and disables the videooutput request signal St84 when the length of the received video streamSt83 is equivalent to the specified presentation time. A video streamequal in length to the specified presentation time is thus decoded bythe video decoder 3800, which outputs the reproduced video signal St104to the synthesizer 3500.

The sub-picture decoder 3100 similarly generates the sub-picture outputrequest signal St86 based on the sub-picture decoding start signal St91,and outputs to the sub-picture buffer 2700. In response to thesub-picture output request signal St86, the sub-picture buffer 2700outputs the sub-picture stream St85 to the sub-picture decoder 3100.Based or the presentation time information contained in the sub-picturestream St85, the sub-picture decoder 3100 decodes a length of thesub-picture stream St85 corresponding to the specified presentation timeto reproduce and supply to the synthesizer 3500 the sub-picture signalSt99.

The synthesizer 3500 superimposes the video signal St104 and sub-picturesignal St99 to generate and output the multi-picture video signal St105to the video data output terminal 3600.

The audio decoder 3200 generates and supplies to the audio buffer 2800the audio output request signal St88 based on the audio stream decodingstart signal St93. The audio buffer 2800 thus outputs the audio streamSt87 to the audio decoder 3200. The audio decoder 3200 decodes a lengthof the audio stream St87 corresponding to the specified presentationtime based on the presentation time information contained in the audiostream St87, and outputs the decoded audio stream St101 to the audiodata output terminal 3700.

It is thus possible to reproduce a user-defined multimedia bitstream MB,in real-time according to a user-defined scenario. More specifically,each time the user selects a different scenario, the authoring decoderDC is able to reproduce the title content desired by the user in thedesired sequence by reproducing the multimedia bitstream MBScorresponding to the selected scenario.

It is therefore possible by means of the authoring system of the presentinvention to generate a multimedia bitstream according to pluraluser-defined scenarios by real-time or batch encoding multimedia sourcedata in a manner whereby the substreams of the smallest editing units(scenes), which can be divided into plural substreams, expressing thebasic title content are arranged in a specific time-base relationship.

The multimedia bitstream thus encoded can then be reproduced accordingto the one scenario selected from among plural possible scenarios. It isalso possible to change scenarios while playback is in progress, i.e.,to select a different scenario and dynamically generate a new multimediabitstream according to the most recently selected scenario. It is alsopossible to dynamically select and reproduce any of plural scenes whilereproducing the title content according to a desired scenario.

It is therefore possible by means of the authoring system of the presentinvention to encode and not only reproduce but to repeatedly reproduce amultimedia bitstream MBS in real-time.

A detail of the authoring system is disclosed in Japanese PatentApplication filed Sep. 27, 1996, and entitled and assigned to the sameassignee as the present application.

Digital Video Disk (DVD)

An example of a digital video disk (DVD) with only one recording surface(a single-sided DVD) is shown in FIG. 4.

The DVD recording medium RC1 in the preferred embodiment of theinvention comprises a data recording surface RS1 to and from which datais written and read by emitting laser beam LS, and a protective layerPL1 covering the data recording surface RS1. A backing layer BL1 is alsoprovided on the back of data recording surface RS1. The side of the diskon which protective layer PL1 is provided is therefore referred to belowas side SA (commonly "side A"), and the opposite side (on which thebacking layer BL1 is provided) is referred to as side SB ("side B").Note that digital video disk recording media having a single datarecording surface RS1 on only one side such as this DVD recording mediumRC1 is commonly called a single-sided single layer disk.

A detailed illustration of area C1 in FIG. 4 is shown in FIG. 5. Notethat the data recording surface RS1 is formed by applying a metallicthin film or other reflective coating as a data layer 4109 on a firsttransparent layer 4108 having a particular thickness T1. This firsttransparent layer 4108 also functions as the protective layer PL1. Asecond transparent substrate 4111 of a thickness T2 functions as thebacking layer BL1, and is bonded to the first transparent layer 4108 bymeans of an adhesive layer 4110 disposed therebetween.

A printing layer 4112 for printing a disk label may also be disposed onthe second transparent substrate 4111 as necessary. Thea printing layer4112 does not usually cover the entire surface area of the secondtransparent substrate 1111 (backing layer BL1), but only the area neededto print the text and graphics of the disk label. The area of secondtransparent substrate 4111 to which the printing layer 4112 is notformed may be left exposed. Light reflected from the data layer 4109(metallic thin film) forming the data recording surface RS1 cantherefore be directly observed where the label is not printed when thedigital video disk is viewed from side SB. As a result, the backgroundlooks like a silver-white over which the printed text and graphics floatwhen the metallic thin film is an aluminum thin film, for example.

Note that it is only necessary to provide the printing layer 4112 whereneeded for printing, and it is not necessary to provide the printinglayer 4112 over the entire surface of the backing layer BL1.

A detailed illustration of area C2 in FIG. 5 is shown in FIG. 6. Pitsand lands are molded to the common contact surface between the firsttransparent layer 4108 and the data layer 4109 on side SA from whichdata is read by emitting a laser beam LS, and data is recorded byvarying the lengths of the pits and lands (i.e., the length of theintervals between the pits). More specifically, the pit and landconfiguration formed on the first transparent layer 4108 is transferredto the data layer 4109. The lengths of the pits and lands is shorter,and the pitch of the data tracks formed by the pit sequences isnarrower, than with a conventional Compact Disc (CD). The surfacerecording density is therefore greatly improved.

Side SA of the first transparent layer 4108 on which data pits are notformed is a flat surface. The second transparent substrate 4111 is forreinforcement, and is a transparent panel made from the same material asthe first transparent layer 4108 with both sides flat. Thicknesses T1and T2 are preferably equal and commonly approximately 0.6 mm, but theinvention shall not be so limited.

As with a CD, information is read by irradiating the surface with alaser beam LS and detecting the change in the reflectivity of the lightspot. Because the objective lens apertures NA can be large and thewavelength 1 of the light beam small in a digital video disk system, thediameter of the light spot Ls used can be reduced to approximately 1/1.6the light spot needed to read a CD. Note that this means the resolutionof the laser beam LS in the DVD system is approximately 1.6 times theresolution of a conventional CD system.

The optical system used to read data from the digital video disk uses ashort 650 nm wavelength red semiconductor laser and an-objective lenswith a 0.6 mm aperture NA. By thus also reducing the thickness T of thetransparent panels to 0.6 mm, more than 5 GB of data can be stored toone side of a 120 mm diameter optical disk.

It is therefore possible to store motion picture (video) images havingan extremely large per unit data size to a digital video disk systemdisk without losing image quality because the storage capacity of asingle-sided, single-layer recording medium RC1 with one data recordingsurface RS1 as thus described is nearly ten times the storage capacityof a conventional CD. As a result, while the video presentation time ofa conventional CD system is approximately 74 minutes if image quality issacrificed, high quality video imacges with a video presentation timeexceeding two hours can be recorded to a DVD.

The digital video disk is therefore well-suited as a recording mediumfor video images.

A digital video disk recording medium with plural recording surfaces RSas described above is shown in FIGS. 7 and 8. The DVD recording mediumRC2 shown in FIG. 7 comprises two recording surfaces, i.e., firstrecording surface RS1 and semi-transparent second recording surface RS2,on the same side, i.e. side SA, of the disk. Data can be simultaneouslyrecorded or reproduced from these two recording surfaces by useingdifferent laser beams LS1 and LS2 for the first recording surface RS1and the second recording surface RS2. It is also possible to read/writeboth recording surfaces RS1 and RS2 using only one of the laser beamsLS1 or LS2. Note that recording media thus comprised are called"single-side, dual-layer disks."

It should also be noted that while two recording surfaces RS1 and RS2are provided in this example, it is also possible to produce digitalvideo disk recording media having more than two recording surfaces RS.Disks thus comprised are known as "single-sided, multi-layer disks."

Though comprising two recording surfaces similarly to the recordingmedia shown in FIG. 7, the DVD recording medium RC3 shown in FIG. 8 hasthe recording surfaces on opposite sides of the disk, i. e., has thefirst data recording surface RS1 on side SA and the second datarecording surface RS2 on side SB. It will also be obvious that whileonly two recording surfaces are shown on one digital video disk in thisexample, more than two recording surfaces may also be formed on adouble-sided digital video disk. As with the recording medium shown inFIG. 7, it is also possible to provide two separate laser beams LS1 andLS2 for recording surfaces RS1 and RS2, or to read/write both recordingsurfaces RS1 and RS2 using a single laser beam. Note that this type ofdigital video disk is called a "double-sided, dual-layer disk." It willalso be obvious that a double-sided digital video disk can be comprisedwith two or more recording surfaces per side. This type of disk iscalled a "double-sided, multi-layer disk."

A plan view from the laser beam LS irradiation side of the recordingsurface RS of the DVD recording medium RC is shown in FIG. 9 and FIG.10. Note that a continuous spiral data recording track TR is providedfrom the inside circumference to the outside circumference of the DVD.The data recording track TR is divided into plural sectors each havingthe same known storage capacity. Note that for simplicity only the datarecording track TR is shown in FIG. 9 with more than three sectors perrevolution.

As shown in FIG. 9, the data recording track TR is normally formedclockwise inside to outside (see arrow DrA) from the inside end point IAat the inside circumference of disk RCA to the outside end point OA atthe outside circumference of the disk with the disk RCA rotatingcounterclockwise RdA. This type of disk RCA is called a clockwise disk,and the recording track formed thereon is called a clockwise track TRA.

Depending upon the application, the recording track TRB may be formedclockwise from outside to inside circumference (see arrow DrB in FIG.10) from the outside end point OB at the outside circumference of diskRCB to the inside end point IB at the inside circumference of the diskwith the disk RCB rotating clockwise RdB. Because the recording trackappears to wind counterclockwise when viewed from the insidecircumference to the outside circumference on disks with the recordingtrack formed in the direction of arrow DrB, these disks are referred toas counterclockwise disk RCB with counterclockwise track TRB todistinguish them from disk RCA in FIG. 9. Note that track directions DrAand DrB are the track paths along which the laser beam travels whenscanning the tracks for recording and playback. Direction of diskrotation RdA in which disk RCA turns is thus opposite the direction oftrack path DrA, and direction of disk rotation RdB in which disk RCBturns is thus opposite the direction of track path DrB.

An exploded view of the single-sided, dual-layer disk RC2 shown in FIG.7 is shown as disk RC2o in FIG. 11. Note that the recording tracksformed on the two recording surfaces run in opposite directions.Specifically, a clockwise recording track TRA as shown in FIG. 9 isformed in clockwise direction DrA on the (lower) first data recordingsurface RS1, and a counterclockwise recording track TRB formed incounterclockwise direction DrB as shown in FIG. 10 is providead on the(upper) second data recording surface RS2. As a result, the outside endpoints OA and OB of the first and second (top and bottom) tracks are atthe same radial position relative to the center axis of the disk RC2o.Note that track paths DrA and DrB of tracks TR are also the dataread/write directions to disk RC. The first and second (top and bottom)recording tracks thus wind opposite each other with this disk RC, i.e.,the track paths DrA and DrB of the top and bottom recording layers areopposite track paths.

Opposite track path type, single-sided, dual-layer disks RC2o rotate indirection RdA corresponding to the first recording surface RS1 with thelaser beam LS travelling along track path DrA to trace the recordingtrack on the first recording surface RS1. When the laser beam LS reachesthe outside end point OA, the laser beam LS can be refocused to endpoint OB on the second recording surface RS2 to continue tracing therecording track from the first to the second recording surfaceuninterrupted. The physical distance between the recording tracks TRAand TRB on the first and second recording surfaces RS1 and RS2 can thusbe instantaneously eliminated by simply adjusting the focus of the laserbeam LS.

It is therefore possible with an opposite track path type, single-sided,dual-layer disk RC2o to easily process the recording tracks disposed tophysically discrete top and bottom recording surfaces as a singlecontinuous recording track. It is therefore also possible in anauthoring system as described above with reference to FIG. 1 tocontinuously record the multimedia bitstream MBS that is the largestmultimedia data management unit to two discrete recording surfaces RS1and RS2 on a single recording medium RC2o.

It should be noted that the tracks on recording surfaces RS1 and RS2 canbe wound in the directions opposite those described above, i.e., thecounterclockwise track TRB may be provided on the first recordingsurface RS1 and the clockwise track TRA on the second recording surfaceRS2. In this cease the direction of disk rotation is also changed to aclockwise rotation RdB, thereby enabling the two recording surfaces tobe used as comprising a single continuous recording track as describedabove. For simplification, a further example of this type of disk istherefore neither shown nor described below.

It is therefore possible by thus constructing the digital video disk torecord the multimedia bitstream MBS for a feature-length title to asingle opposite track path type, single-sided, du-al-layer disk RC2o.Note that this type of digital video disk medium is called asingle-sided dual-layer disk with opposite track paths.

Another example of the single-sided, dual-layer DVD recording medium RC2shown in FIG. 7 is shown as disk RC2p in FIG. 12. The recording tracksformed on both first and second recording surfaces RS1 and RS2 areclockwise tracks TRA as shown in FIG. 9. In this case, the single-sided,dual-layer disk RC2p rotates counterclockwise in the direction of arrowRdA, and the direction of laser beam LS travel is the same as thedirection of the track spiral, i.e., the track paths of the top andbottom recording surfaces are mutually parallel (parallel track paths).The outside end points OA of both top and bottom tracks are againpreferably positioned at the same radial position relative to the centeraxis of the disk RC2p as described above. As also described above withdisk RC2o shown in FIG. 11, the access point can be instantaneouslyshifted from outside end point OA of track TRA on the first recordingsurface RS1 to the outside end point OA of track TRA on the secondrecording surface RS2 by appropriately adjusting the focus of the laserbeam LS at outside end point OA.

However, for the laser beam LS to continuously access the clockwiserecording track TRA on the second recording surface RS2, the recordingmedium RC2p must be driven in the opposite direction (clockwise,opposite direction RdA). Depending-on the radial position of the laserbeam LS, however, it is inefficient to change the rotational directionof the recording medium. As shown by the diagonal arrow in FIG. 12, thelaser beam LS is therefore moved from The outside end point OA of thetrack on the first recording surface RS1 to the inside end point IA ofthe track on the second recording surface RS2 to use these physicallydiscrete recording tracks as one logically continuous recording track.

Rather than using the recording tracks on top and bottom recordingsurfaces as one continuous recording track, it is also possible to usethe recording tracks to record the multimedia bitstreams MBS fordifferent titles.

This type of digital video disk recording medium is called a"single-sided, dual-layer disk with parallel track paths."

Note that if the direction of the tracks formed on the recordingsurfaces RS1 and RS2 is opposite that described above, i.e.,counterclockwise recording tracks TRB are formed, disk operation remainsthe same as that described above except for the direction of diskrotation, which is clockwise as shown by arrow RdB.

Whether using clockwise or counterclockwise recording tracks, thesingle-sided, dual-layer disk RC2p with parallel track paths thusdescribed is well-suited to storing on a single disk encyclopedia andsimilar multimedia bitstreams comprising multiple titles that arefrequently and randomly accessed.

An exploded view-of the dual-sided single-layer DVD recording medium RC3comprising one recording surface layer RS1 and RS2 on (each side asshown in FIG. 8 is shown as DVD recording medium RC3s in FIG. 13.Clockwise recording track TRA is provided on the one recording surfaceRS1, and a counterclockwise recording track TRB is provided on the otherrecording surface RS2. As in the preceding recording media, the outsideend points OA and OB of the recording tracks on each recording surfaceare preferably positioned at the same radial position relative to thecenter axis of the DVD recording medium RC3s.

Note that while the recording tracks on these recording surfaces R31 andRS2 rotate in opposite directions, the track paths are symmetrical. Thistype of recording medium is therefore known as a double-sided dual layerdisk with symmetrical track paths. This double-sided dual layer diskwith symmetrical track paths RC3s rotates in direction RdA whenreading/writing the first recording surface RS1. As a result, the trackpath on the second recording surface RS2 on the opposite side isopposite the direction DrB in which the track winds, i.e., directionDrA. Accessing both recording surfaces RS1 and RS2 using a single laserbeam LS is therefore not realistic irrespective of whether access iscontinuous or non-continuous. In addition, a multimedia bitstream MBS isseparately recorded to the recording surfaces on the first and secondsides of the disk.

A different example of the double-sided single layer disk RC3 shown inFIG. 8 is shown in FIG. 14 as disk RC3a. Note that this disk comprisesclockwise recording tracks TRA as shown in FIG. 9 on both recordingsurfaces RS1 and RS2. As with the preceding recording media, the outsideend points OA and OA of the recording tracks on each recording surfaceare preferably positioned at the same radial position relative to thecenter axis of the DVD recording medium RC3a. Unlike the double-sideddual layer disk with symmetrical track paths RC3s described above, thetracks on these recording surfaces RS1 and RS2 are asymmetrical. Thistype of disk is therefore known as a double-sided dual layer disk withasymmetrical track paths.

This double-sided dual layer disk with asymmetrical track paths RC3arotates in direction RdA when reading/writing the first recordingsurface RS1. As a result, the track path on the second recording surfaceRS2 on the opposite side is opposite the direction DrA in which thetrack winds, i.e., direction DrB.

This means that if a laser beam LS is driven continuously from theinside circumference to the outside circumference on the first recordingsurface RS1, and then from the outside circumference to the insidecircumference on the second recording surface RS2, both sides of therecording medium RC3a can be read/written without turning the disk overand without providing different laser beams for the two sides.

The track paths for recording surfaces RS1 and RS2 are also the samewith this double-sided dual layer disk with asymmetrical track pathsRC3a. As a result, it is also possible to read/write both sides of thedisk without providing separated laser beams for each side if therecording medium RC3a is turned over between sides, and the read/writeapparatus can therefore be constructed economically.

It should be noted that this recording medium remains functionallyidentical even if counterclockwise recording track TRB is provided inplace of clockwise recording track TRA on both recording surfaces RS1and RS2.

As described above, the true value of a DVD system whereby the storagecapacity of the recording medium can be easily increased by using amultiple layer recording surface is realized in multimedia applicationswhereby plural video data units, plural audio data units, and pluralgraphics data units recorded to a single disk are reproduced throughinteractive operation by the user.

It is therefore possible to achieve one long-standing desire of software(programming) providers, specifically, to provide programming contentsuch as a commercial movie on a single recording medium in pluralversions for different language and demographic groups while retainingthe image quality of the original.

Parental Control

Content providers of movie and video titles have conventionally had toproduce, supply, and manage the inventory of individual titles inmultiple languages, typically the language of each distribution market,and multi-rated title packages conforming to the parental control(censorship) regulations of individual countries in Europe and NorthAmerica. The time and resources required for this are significant. Whilehigh image quality is obviously important, the programming content mustalso be consistently reproducible.

The digital video disk recording medium is close to solving theseproblems.

Multiple Angles

One interactive operation widely sought in multimedia applications todayis for the user to be able to change the position from which a scene isviewed during reproduction of that scene. This capability is achieved bymeans of the multiple angle function.

This multiple angle function makes possible applications whereby, forexample, a user can watch a baseball game from different angles (orvirtual positions in the stadium), and can freely switch between theviews while viewing is in progress. In this example of a baseball game,the available angles may include a position behind the backstop centeredon the catcher, batter, and pitcher; one from behind the backstopcentered on a fielder, the pitcher, and the catcher; and one from centerfield showing the view to the pitcher and catcher.

To meet these requirements, the digital video disk system uses MPEG, thesame basic standard format used with Video-Cds to record the video,audio, graphics, and other signal data. Because of the differences instorage capacity, transfer rates, and signal processing performancewithin the reproduction apparatus, DVD uses MPEG2, the compressionmethod and data format of which differ slightly from the MPEG1 formatused with Video-Cds.

It should be noted that the content of and differences between the MPEG1and MPEG2 standards have no direct relationship to the intent of thepresent invention, and further description is therefore omitted below(for more information, see MPEG specifications ISO-11172 and ISO-13818).

The data structure of the DVD system according to the present inventionis described in detail below with reference to FIGS. 16, 17, 18, 19, 20,and 21.

Multi-scene Control

A fully functional and practical parental lock playback function andmulti-angle scene playback function must enable the user to modify thesystem output in minor, subtle ways while still presenting substantiallythe same video and audio output. If these functions are achieved bypreparing and recording separate titles satisfying each of the manypossible parental lock and multi-angle scene playback requests, titlesthat are substantially identical and differ in only minor ways must berecorded to the recording medium. This results in identical data beingrepeatedly recorded to the larger part of the recording medium, andsignificantly reduces the utilization efficiency of the availablestorage capacity. More particularly, it is virtually impossible torecord discrete titles satisfying every possible request even using themassive capacity of the digital video disk medium. While it may beconcluded that this problem can be easily solved by increasing thecapacity of the recording medium, this is an obviously undesirablesolution when the effective use of available system resources isconsidered.

Using multi-scene control, the concept of which is described in anothersection below, in a DVD system, it is possible to dynamically constructtitles for numerous variations of the same basic content using thesmallest possible amount of data, and thereby effectively utilize theavailable system resources (recording medium). More specifically, titlesthat can be played back with numerous variations are constructed frombasic (common) scene periods containing data common to each title, andmulti-scene periods comprising groups of different scenes correspondingto the various requests. During reproduction, the user is able to freelyand at any time select particular scenes from the multi-scene periods todynamically construct a title conforming to the desired content, e.g., atitle omitting certain scenes using the parental lock control function.

Note that multi-scene control enabling a parental lock playback controlfunction and multi-angle scene playback is described in another sectionbelow with reference to FIG. 21.

Data Structure of the DVD System

The data structure used in the authoring system of a digital video discsystem according to the present invention is shown in FIG. 22. To recorda multimedia bitstream MBS, this digital video disk system divides therecording medium into three major recording areas, the lead-in area LI,the volume space VS, and the lead-out area LO.

The lead-in area LI is provided at the inside circumference area of theoptical disk. In the disks described with reference to FIGS. 9 and 10,the lead-in area LI is positioned at the inside end points IA and IB ofeach track. Data for stabilizing the operation of the reproducingapparatus when reading starts is written to the lead-in area LI.

The lead-out area LO is correspondingly located at the outsidecircumference of the optical disk, i.e., at outside end points OA and OBof each track in the disks described with reference to FIGS. 9 and 10.Data identifying the end of the volume space VS is recorded in thislead-out area LO.

The volume space VS is located between the lead-in area LI and lead-outarea LO, and is recorded as a one-dimensional array of n+1 (where n isan integer greater than or equal to zero) 2048-byte logic sectors LS.The logic sectors LS are sequentially number #0, #1, #2, . . . #n. Thevolume space VS is also divided into a volume and file structuremanagement area VFS and a file data structure area FDS.

The volume and file structure management area VFS comprises m+1 logicsectors LS#0 to LS#m (where m is an integer greater than or equal tozero and less than n. The file data structure FDS comprises n-m logicsectors LS #m+1 to LS #n.

Note that this file data structure area FDS corresponds to themultimedia bitstream MBS shown in FIG. 1 and described above.

The volume file structure VFS is the file system for managing the datastored to the volume space VS as files, and is divided into logicsectors LS#0-LS#m where m is the number of sectors required to store alldata needed to manage the entire disk, and is a natural number less thann. Information for the files stored to the file data structure area FDSis written to the volume file structure VFS according to a knownspecification such as ISO-9660 or IS0-13346.

The file data structure area FDS comprises n-m logic sectors LS#m-LS#n,each comprising a video manager VMG sized to an integer multiple of thelogic sector (2048×I, where I is a known integer), and k video titlesets VTS #1-VTS#k (where k is a natural number less than 100).

The video manager VMG stores the title management information for theentire disk, and information for building a volume menu used to set andchange reproduction control of the entire volume.

Any video title set VTS #k is also called a "video file" representing atitle comprising video, audio, and/or still image data.

The internal structure of each video title set VTS shown in FIG. 22 isshown in FIG. 16. Each video title set VTS comprises VTS informationVTSI describing the management information for the entire disk, and theVTS title video objects VOB (VTSTT₋₋ VOBS), i.e., the system stream ofthe multimedia bitstream. The VTS information VTSI is described firstbelow, followed by the VTS title VOBS.

The VTS information primarily includes the VTSI management table VTSI₋₋MAT and VTSPGC information table VTS₋₋ PGCIT.

The VTSI management table VTSI₋₋ MAT stores such information as theinternal structure of the video title set VTS, the number of selectableaudio streams contained in the video title set VTS, the number ofsub-pictures, and the video title set VTS location (storage address).

The VTSPGC information table VTS₋₋ PGCIT records i (where i is a naturalnumber) program chain (PGC) data blocks VTS₋₋ PGCI #1-VTS₋₋ PGCI #i forcontrolling the playback sequence. Each of the table entries VTS₋₋ PGCI#i is a data entry expressing the program chain, and comprises j (wherej is a natural number) cell playback information blocks C₋₋ PBI #1-C₋₋PBI #j. Each cell playback information block C₋₋ PBI #j contains theplayback sequence of the cell and playback control information.

The program chain PGC is a conceptual structure describing the story ofthe title content, and therefore defines the structure of each title bydescribing the cell playback sequence. Note that these cells aredescribed in detail below.

If, for example, the video title set information relates to the menus,the video title set information VTSI is stored to a buffer in theplayback device when playback starts. If the user then presses a MENUbutton on a remote control device, for example, during playback, theplayback device references the buffer to fetch the menu information anddisplay the top menu #1. If the menus are hierarchical, the main menustored as program chain information VTS₋₋ PGCI #1 may be displayed, forexample, by pressing the MENU button, VTS₋₋ PGCI #2-#9 may correspond tosubmenus accessed using the numeric keypad on the remote control, andVTS₋₋ PGCI #10 and higher may correspond to additional submenus furtherdown the hierarchy. Alternatively, VTS₋₋ PCCI #1 may be the top menudisplayed by pressing the MENU button, while VTS₋₋ PGCI #2 and highermay be voice guidance reproduced by pressing the corresponding numerickey.

The menus themselves are expressed by the plural program chains definedin this table. As a result, the menus may be freely constructed invarious ways, and shall not be limited to hierarchical ornon-hierarchical menus or menus containing voice guidance.

In the case of a movie, for example, the video title set informationVTSI is stored to a buffer in the playback device when playback starts,the playback device references the cell playback sequence described bythe program chain PGC, and reproduces the system stream.

The "cells" referenced here may be all or part of the system stream, andare used as access points during playback. Cells can therefore be used,for example, as the "chapters" into which a title may be divided.

Note that each of the PGC information entries C₋₋ PBI #j contain bothcell playback processing information and a cell information table. Thecell playback processing information comprises the processinginformation needed to reproduce the cell, such as the presentation timeand number of repetitions. More specifically, this information includesthe cell block mode CBM, cell block type CBT, seamless playback flagSPF, interleaved allocation flag IAF, STC resetting flag STCDF, cellpresentation time C₋₋ PBTM, seamless angle change flag SACF, first cellVOBU start address C₋₋ FVOBU₋₋ SA, and the last cell VOBU start addressC₋₋ LVOBU₋₋ SA.

Note that seamless playback refers to the reproduction in a digitalvideo disk system of multimedia data including video, audio, andsub-picture data without intermittent breaks in the data or information.Seamless playback is described in detail in another section below withreference to FIG. 23 and FIG. 24.

The cell block mode CBM indicates whether plural cells constitute onefunctional block. The cell playback information of each cell in afunctional block is arranged consecutively in the PGC information. Thecell block mode CBM of the first cell playback information in thissequence contains the value of the first cell in the block, and the cellblock mode CBM of the last cell playback information in this sequencecontains the value of the last cell in the block. The cell block modeCBM of each cell arrayed between these first and last cells contains avalue indicating that the cell is a cell between these first and lastcells in that block.

The cell block type CBT identifies the type of the block indicated bythe cell block mode CBM. For example, when a multiple angle function isenabled, the cell information corresponding to each of the reproducibleangles is programmed as one of the functional blocks mentioned above,and the type of these functional blocks is defined by a valueidentifying "angle" in the cell block type CBT for each cell in thatblock.

The seamless playback flag SPF simply indicates whether thecorresponding cell is to be linked and played back seamlessly with thecell or cell block reproduced immediately therebefore. To seamlesslyreproduce a given cell with the preceding cell or cell block, theseamless playback flag SPF is set to 1 in the cell playback informationfor that cell; otherwise SPF is set to 0.

The interleaved allocation flag IAF stores a value identifying whetherthe cell exists in a contiguous or interleaved block. If the cell ispart of an interleaved block, the flag IAF is set to 1; otherwise it isset to 0.

The STC resetting flag STCDF identifies whether the system time clockSTC used for synchronization must be reset when the cell is played back;when resetting the system time clock STC is necessary, the STC resettingflag STCDF is set to 1.

The seamless angle change flag SACF stores a value indicating whether acell in a multi-angle period should be connected seamlessly at an anglechange. If the angle change is seamless, the seamless angle change flagSACF is set to 1; otherwise it is set to 0.

The cell presentation time C₋₋ PBTM expresses the cell presentation timewith video frame precision.

The first cell VOBU start address C₋₋ FVOBU₋₋ SA is the VOBU startaddress of the first cell in a block, and is also expressed as thedistance from the logic sector of the first cell in the VTS title VOBS(VTSTT₋₋ VOBS) as measured by the number of sectors.

The last cell VOBU start address C₋₋ LVOBU₋₋ SA is the VOBU startaddress of the last cell in the block. The value of this address isexpressed as the distance from the logic sector of the first cell in theVTS title VOBS (VTSTT₋₋ VOBS) as measured by the number of sectors.

The VTS title VOBS (VTSTT₋₋ VOBS), i.e., the multimedia system streamdata, is described next. The system stream data VTSTT₋₋ VOBS comprises i(where i is a natural number) system streams SS, each of which isreferred to as a "video object" (VOB). Each video object VOB #1-VOB #icomprises at least one video data block interleaved with up to a maximumeight audio data blocks and up to a maximum 32 sub-picture data blocks.

Each video object VOB comprises q (where q is a natural number) cellsC#1-C#q. Each cell C comprises r (where r is a natural number) videoobject units VOBU #1-VOBU #r.

Each video object unit VOBU comprises plural groups₋₋ of₋₋ pictures GOP,and the audio and sub-pictures corresponding to the playback of saidplural groups₋₋ of₋₋ pictures GOP. Note that the group₋₋ of₋₋ picturesGOP corresponds to the video encoding refresh cycle. Each video objectunit VOBU also starts with an NV pack, i.e., the control data for thatVOBU.

The structure of the navigation packs NV is described with reference toFIG. 19.

Before describing the navigation pack NV, the internal structure of thevideo zone VZ (see FIG. 22), i.e., the system stream St35 encoded by theauthoring encoder EC described with reference to FIG. 25, is describedwith reference to FIG. 17. Note that the encoded video stream St15 shownin FIG. 17 is the compressed one-dimensional video data stream encodedby the video encoder 300. The encoded audio stream St19 is likewise thecompressed one-dimensional audio data stream multiplexing the right andleft stereo audio channels encoded by the audio encoder 700. Note thatthe audio signal shall not be Limited to a stereo signal, and may alsobe a multichannel surround-sound signal.

The system stream (title editing unit VOB) St35 is a one dimensionalarray of packs with a byte size corresponding to the logic sectors LS #nhaving a 2048-byte capacity as described using FIG. 22. A stream controlpack is placed at the beginning of the title editing unit (VOB) St35,i.e., at the beginning of the video object unit VOBU. This streamcontrol pack is called the "navigation pack NV", and records the dataarrangement in the system stream and other control information.

The encoded video stream St15 and the encoded audio stream St19 arepacketized in byte units corresponding to the system stream packs. Thesepackets are shown in FIG. 17 as packets V1, V2, V3, V4 . . . and A1, A2,A3 . . . . As shown in FIG. 17, these packets are interleaved in theappropriate sequence as system stream St35, thus forming a packetstream, with consideration given to the decoder buffer size and the timerequired by the decoder to expand the video and audio data packets. Inthe example shown in FIG. 17, the packet stream is interleaved in thesequence V1, V2, A1, V3, V4, A2 . . . .

Note that the sequence shown in FIG. 17 interleaves one video data unitwith one audio data unit. Significantly increased recording/playbackcapacity, high speed recording/playback, and performance improvements inthe signal processing LSI enable the DVD system to record plural audiodata and plural sub-picture data (graphics data) to one video data unitin a single interleaved MPEG system stream, and thereby enable the userto select the specific audio data and sub-picture data to be reproducedduring playback. The structure of the system stream used in this type ofDVD system is shown in FIG. 18 and described below.

As in FIG. 17, the packetized encoded video stream St15 is shown in FIG.18 as V1, V2, V3, V4, . . . . In this example, however, there is notjust one encoded audio stream St19, but three encoded audio streamsSt19A, St19B, and St19C input as the source data. There are also twoencoded sub-picture streams St17A and St17B input as the source datasub-picture streams. These six compressed data streams, St15, St19A,3t19B, St19C, St17A and St17B, are interleaved to a single system streamSt35.

The video data is encoded according to the MPEG specification with thegroup₋₋ of₋₋ pictures GOP being the unit of compression. In general,each group₋₋ of₋₋ pictures GOP contains 15 frames in the case of an NTSCsignal, but the specific number of frames compressed to one GOP isvariable. The stream management pack, which describes the managementdata containing, for example, the relationship between interleaved data,is also interleaved at the GOP unit interval. Because the group₋₋ of₋₋pictures GOP unit is based on the video data, changing the number ofvideo frames per GOP unit changes the interval of the stream managementpacks. This interval is expressed in terms of the presentation time onthe digital video disk within a range from 0.4 sec. to 1.0 sec.referenced to the GOP unit. If the presentation time of contiguousplural GOP units is less than 1 sec., the management data packs for thevideo data of the plural GOP units is interleaved to a single stream.

These management data packs are referred to as navigation packs NV inthe digital video disk system. The data from one navigation pack NV tothe packet immediately preceding the next navigation pack NV forms onevideo object unit VOBU. In general, one contiguous playback unit thatcan be defined as one scene is called a video object VOB, and each videoobject VOB contains plural video object units VOBU. Data sets of pluralvideo objects VOB form a VOB set (VOBS). Note that these data units werefirst used in the digital video disk.

When plural of these data streams are interleaved, the navigation packsNV defining the relationship between the interleaved packs must also beinterleaved at a defined unit known as the pack number unit. Eachgroup₋₋ of₋₋ pictures GOP is normally a unit containing approximately0.5 sec. of video data, which is equivalent to the presentation timerequired for 12-15 frames, and one navigation pack NV is generallyinterleaved with the number of data packets required for thispresentation time.

The stream management information contained in the interleaved video,audio, and sub-picture data packets constituting the system stream isdescribed below with reference to FIG. 19 As shown in FIG. 19, the datacontained in the system stream is recorded in a format packed orpacketized according to the MPEG2 standard. The packet structure isessentially the same for video, audio, and sub-picture data. One pack inthe digital video disk system has a 2048 byte capacity as describedabove, and contains a pack header PKH and one packet PES; each packetPES contains a packet header PTH and data block.

The pack header PKH records the time at which that pack is to be sentfrom stream buffer 2400 to system decoder 2500 (see FIG. 26), i.e., thesystem clock reference SCR defining the reference time for synchronizedaudio-visual data playback. The MPEG standard assumes that the systemclock reference SCR is the reference clock for the entire decoderoperation. With such disk media as the digital video disk, however, timemanagement specific to individual disk players can be used, and areference clock for the decoder system is therefore separately provided.

The packet header PTH similarly contains a presentation time stamp PTSand a decoding time stamp DTS, both of which are placed in the packetbefore the access unit (the decoding unit). The presentation time stampPTS defines the time at which the video data or audio data contained inthe packet should be output as the playback output after being decoded,and the decoding time stamp DTS defines the time at which the videostream should be decoded. Note that the presentation time stamp PTSeffectively defines the display start timing of the access unit, and thedecoding time stamp DTS effectively defines the decoding start timing ofthe access unit. If the PTS and DTS are the same time, the DTS isomitted.

The packet header PTH also contains an 8-bit field called the stream IDidentifying the packet type, i.e., whether the packet is a video packetcontaining a video data stream, a private packet, or an MPEG audiopacket.

Private packets under the MPEG2 standard are data packets of which thecontent can be freely defined. Private packet 1 in this embodiment ofthe invention is used to carry audio data other than the MPEG audiodata, and sub-picture data; private packet 2 carries the PCI packet andDSI packet.

Private packets 1 and 2 each comprise a packet header, private dataarea, and data area. The private data area contains an 8-bit sub-streamID indicating whether the recorded data is audic) data or sub-picturedata. The audio data defined by private packet 2 may be defined as anyof eight types #0-#7 of linear PCM or AC-3 encoded data. Sub-picturedata may be defined as one of up to 32 types #0-#31.

The data area is the field to which data compressed according to theMPEG2 specification is written if the stored data is video data; linearPCM, AC-3, or MPEG encoded data is written if audio data is stored; orgraphics data compressed by runlength coding is written if sub-picturedata is stored.

MPEG2-compressed video data may be compressed by constant bit rate (CBR)or variable bit rate (VBR) coding. With constant bit rate coding, thevideo stream is input continuously to the video buffer at a constantrate. This contrasts with variable bit rate coding in which the videostream is input intermittently to the video buffer, thereby making itpossible to suppress the generation of unnecessary code. Both constantbit rate and variable bit rate coding can be used in the digital videodisk system.

Because MEIEG video data is compressed with variable length coding, thedata quantity in each group₋₋ of₋₋ pictures GOP is not constant. Thevideo and audio decoding times also differ, and the time-baserelationship between the video and audio data read from an optical disk,and the time-base relationship between the video and audio data outputfrom the decoder, do not match. The method of time-base synchronizingthe video and audio data is therefore described in detail below withreference to FIG. 26, but is described briefly below based on constantbit rate coding.

The navigation pack NV structure is shown in FIG. 20. Each navigationpack NV starts with a pack header PKH, and contains a PCI packet and DSIpacket.

As described above, the pack header PKH records the time at which thatpack is to be sent from stream buffer 2400 to system, decoder 2500 (seeFIG. 26 ), i.e., the system clock reference SCR defining the referencetime for synchronized audio-visual data playback.

Each PCI packet contains PCI General Information (PCI₋₋ GI) and AngleInformation for Non-seamless playback (NMSL₋₋ AGLI).

The PCI General Information (PCI₋₋ GI) declares the display time of thefirst video frame (the Start PTM of VOBU (VOBU₋₋ S₋₋ PTM)), and thedisplay time of the last video frame (End PTM of VOBU (VOBU₋₋ E₋₋ PTM)),in the corresponding video object unit VCBU with system clock precision(90 Khz).

The Angle Information for Non-seamless playback (NMSL₋₋ AGLI) states theread start address of the corresponding video object unit VOBU when theangle is changed expressed as the number of sectors from the beginningof the video object VOB. Because there are nine or fewer angles in thisexample, there are nine angle address declaration cells: DestinationAddress of Angle Cell #1 for Non-seamless playback (NMSL₋₋ AGL₋₋ C1₋₋DSTA) to Destination Address of Angle Cell #9 for Non-seamless playback(NMSL₋₋ AGL₋₋ C9₋₋ DSTA).

Each DSI packet contains DSI General Information (DSI₋₋ GI), SeamlessPliayback Information (SML₋₋ PBI), and Angle Information for Seamlessplayback (SML₋₋ AGLI).

The DSI General Information (DSI₋₋ GI) declares the address of the lastpack in the video object unit VOBU, i. e., the End Address for VOB(VOBU₋₋ EA), expressed as the number of sectors from the beginning ofthe video object unit VOBU.

While seamless playback is described in detail later, it should be notedthat the continuously read data units must be interleaved (multiplexed)at the system stream level as an interleaved unit ILVU in order toseamlessly reproduce split or combined titles. Plural system streamsinterleaved with the interleaved unit ILVU as the smallest unit aredefined as an interleaved block.

The Seamless Playback Information (SML₋₋ PBI) is declared to seamlesslyreproduce the stream interleaved with the interleaved unit ILVU as thesmallest data unit, and contains an Interleaved Unit Flag (ILVU flag)identifying whether the corresponding video object unit VOBU is aninterleaved block. The ILVU flag indicates whether the video object unitVOBU is in an interleaved block, and is set to 1 when it is. Otherwisethe ILVU flag is set to 0.

When a video object unit VOBU is in an interleaved block, a Unit ENDflag is declared to indicate whether the video object unit VOBU is thelast VOBU in the interleaved unit ILVU. Because the interleaved unitILVU is the data unit for continuous reading, the Unit END flag is setto 1 if the VOEU currently being read is the last VOBU in theinterleaved unit ILVU. Otherwise the Unit END flag is set to 0.

An Interleaved Unit End Address (ILVU₋₋ EA) identifying the address ofthe last pack in the ILVU to which the VOBU belongs, and the startingaddress of the next interleaved unit ILVU, Next Interleaved Unit StartAddress (NT₋₋ ILVU₋₋ SA), are also declared when a video object unitVOBU is in an interleaved block. Both the Interleaved Unit End Address(ILVJ₋₋ EA) and Next Interleaved Unit Start Address (NT₋₋ ILVU₋₋ SA) areexpressed as the number of sectors from the navigation pack NV of thatVOBU.

When two system streams are seamlessly connected but the audiocomponents of the two system streams are not contiguous, particularlyimmediately before and after the seam, it is necessary to pause theaudio output to synchronize the audio and video components of the systemstream following the seam. Note that non-contiguous audio may resultfrom different audio signals being recorded with the corresponding videoblocks. With an NTSC signal, for example, the video frame cycle isapproximately 33.33 msec while the AC-3 audio frame cycle is 32 msec.

To enable this resynchronization, audio reproduction stopping times 1and 2, i.e., Audio Stop PTM 1 in VOB (VOB₋₋ A₋₋ STP₋₋ PTM1), and AudioStop PTM2 in VOB (VOB₋₋ A₋₋ STP₋₋ PTM2), indicating the time at whichthe audio is to be paused; and audio reproduction stopping periods 1 and2, i.e., Audio Gap Length 1 in VOB (VOB₋₋ A₋₋ GAP₋₋ LEN1) and Audio GapLength 2 in VOB (VOB₋₋ A₋₋ GAP₋₋ LEN2), indicating for how long theaudio is to be paused, are also declared in the DSI packet. Note thatthese times are specified at the system clock precision (90 Khz).

The Angle Information for Seamless playback (SML₋₋ AGLI) declares theread start address when the angle is changed. Note that: this field isvalid when seamless, multi-angle control is enabled. This address isalso expressed as the number of sectors from the navigation pack NV ofthat VOBU. Because there are nine or fewer angles, there are nine angleaddress declaration cells: Destination Address of Angle Cell #1 forSeamless playback (SML₋₋ AGL₋₋ C1₋₋ DSTA) to Destination Address ofAngle Cell #9 for Seamless playback (SML₋₋ AGL₋₋ C9₋₋ DSTA).

Note also that each title is edited in video object (VOB) units.Interleaved video objects (interleaved title editing units) arereferenced as "VOBS"; and the encoded range of the source data is theencoding unit.

DVD Encoder

A preferred embodiment of a digital video disk system authoring encoderECD in which the multimedia bitstream authoring system according to thepresent invention is applied to a digital video disk system is describedbelow and shown in FIG. 25. It will be obvious that the authoringencoder ECD applied to the digital video disk system, referred to belowas a DVD encoder, is substantially identical to the authoring encoder ECshown in FIG. 2. The basic difference between these encoders is thereplacement in the DVD encoder ECD of the video zone formatter 1300 ofthe authoring encoder EC above with a VOB buffer 1000 and formatter1100. It will also be obvious that the bitstream encoded by this DVDencoder ECD is recorded to a digital video disk medium M. The operationof this DVD encoder ECD is therefore described below in comparison withthe authoring encoder EC described above.

As in the above authoring encoder EC, the encoding system controller 200generates control signals St9, St11, St13, St21, St23, St25, St33, andSt39 based on the scenario data St7 describing the user-defined editinginstructions input from the scenario editor 100, and controls the videoencoder 300, sub-picture encoder 500, and audio encoder 700 in the DVDencoder ECD. Note that the user-defined editing instructions in the DVDencoder ECD are a superset of the editing instructions of the authoringencoder EC described above.

Specifically, the user-defined editing instructions (scenario data St7)in the DVD encoder ECD similarly describe what source data is selectedfrom all or a subset of the source data containing plural titles withina defined time period, and how the selected source data is reassembledto reproduce the scenario (sequence) intended by the user. The scenariodata St7 of the DVD encoder ECD, however, further contains suchinformation as: the number of streams contained in the editing units,which are obtained by splitting a multi-title source stream into blocksat a constant time interval; the number of audio and sub-picture datacells contained in each stream, and the sub-picture display time andperiod; whether the title is a multi-rated title enabling parental lockcontrol; whether the user content is selected from plural streamsincluding, for example, multiple viewing angles; and the method ofconnecting scenes when the angle is switched among the multiple viewingangles.

The scenario data St7 of the DVD encoder ECD also contains controlinformation on a video object VOB unit basis. This information isrequired to encode the media source stream, and specifically includessuch information as whether there are multiple angles or parentalcontrol features. When multiple angle viewing is enabled, the scenariodata St7 also contains the encoding bit rate of each stream consideringdata interleaving and the disk capacity, the start and end times of eachcontrol, and whether a seamless connection should be made between thepreceding and following streams.

The encoding system controller 200 extracts this information from thescenario data St7, and generates the encoding information table andencoding parameters required for encoding control. The encodinginformation table and encoding parameters are described with referenceto FIGS. 27, 28, and 29 below.

The stream encoding data St33 contains the system stream encodingparameters and system encoding start and end timing values required bythe DVD system to generate the VOBS. These system stream encodingparameters include the conditions for cornecting one video object VOBwith those before and after, the number of audio streams, the audioencoding information and audio Ids, the number of sub-pictures and thesub-picture Ids, the video playback starting time information VPTS, andthe audio playback starting time information APTS.

The title seaquence control signal St39 supplies the multimediabitstream MBS formatting start and end timing information and formattingparameters declaring the reproduction control information and interleaveinformation.

Based on the video encoding parameter and encoding start/end timingsignal St9, the video encoder 300 encodes a specific part of the videostream St1 to generate an elementary stream conforming to the MPEG2Video standard defined in ISO-13818. This elementary stream is output tothe video stream buffer 400 as encoded video stream St1S.

Note that while the video encoder 300 generates an elementary streamconforming to the MPEG2 Video standard defined in ISO-13818, specificencoding parameters are input via the video encoding parameter signalSt9, including the encodirng start and end timing, bit rate, theencoding conditions for the encoding start and end, the material type,including whether the material is an NTSC or PAL video signal ortelecine converted material, and whether the encoding irode is set foreither open GOP or closed GOP encoding.

The MPEG2 coding method is basically an interframe coding method usingthe correlation between frames for maximum signal compression, i.e., theframe being coded (the target frame) is coded by referencing framesbefore and/or after the target frame. However, intra-coded frames, i.e., frames that are coded based solely on the content of-the targetframe, are also inserted to avoid error propagation and enableaccessibility from mid-stream (random access). The coding unitcontaining at least one intra-coded frame ("intra-frame") is called agroup₋₋ of₋₋ pictures GOP.

A group₋₋ of₋₋ pictures GOP in which coding is closed completely withinthat GOP is known as a "closed GOP." A group₋₋ of₋₋ pictures GOPcontaining a frame coded with reference to a frame in a preceding orfollowing (ISO-13818 DOES NOT LIMIT P- and B-picture CODING toreferencing PAST frames) group₋₋ of₋₋ pictures GOP is an "open GOP." Itis therefore possible to playback a closed GOP using only that GOP.Reproducing an open GOP, however, also requires the presence of thereferenced GOP, generally the GOP preceding the open GOP.

The GOP is often used as the access unit. For example, the GOP may beused as the playback start point for reproducing a title from themiddle, as a transition point in a movie, or for fast-forward play andother special reproduction modes. High speed reproduction can beachieved in such cases by reproducing only the intra-frame coded framesin a GOP or by reproducing only frames in GOP units.

Based on the sub-picture stream encoding parameter signal St11, thesub-picture encoder 500 encodes a specific part of the sub-picturestream St3 to generate a variable length coded bitstream of bitmappeddata. This variable length coded bitstream data is output as the encodedsub-picture stream St17 to the sub-picture stream buffer 600.

Based on the audio encoding parameter signal St13, the audio encoder 700encodes a specific part of the audio stream St5 to generate the encodedaudio data. This encoded audio data may be data based on the MPEG1 audiostandard defined in ISO-11172 and the MPEG2 audio standard defined inISO-13818, AC-3 audio data, or PCM (LPCM) data. Note that the methodsand means of encoding audio data according to these standards are knownand commonly available.

The video stream buffer 400 is connected to the video encoder 300 and tothe encoding system controller 200. The video stream buffer 400 storesthe encoded video stream St15 input from the video encoder 300, andoutputs the stored encoded video stream St15 as the time-delayed encodedvideo stream St27 based on the timing signal St21 supplied from theencoding system controller 200.

The sub-picture stream buffer 600 is similarly connected to thesub-picture encoder 500 and to the encoding system controller 200. Thesub-picture stream buffer 600 stores the encoded sub-picture stream St17input from the sub-picture encoder 500, and then outputs the storedencoded sub-picture stream St17 as time-delayed encoded sub-picturestream St29 based on the timing signal St23 supplied from the encodingsystem controller 200.

The audio stream buffer 800 is similarly connected to the audio encoder700 and to the encoding system controller 200. The audio stream buffer800 stores the encoded audio stream St19 input from the audio encoder700, and then outputs the encoded audio stream St19 as the time-delayedencoded audio stream St31 based on the timing signal St25 supplied fromthe encoding system controller 200.

The system encoder 900 is connected to the video stream buffer 400,sub-picture stream buffer 600, audio stream buffer 800, and the encodingsystem controller 200, and is respectively supplied thereby with thetime-delayed encoded video stream St27, time-delayed encoded sub-picturestream St29, time-delayed encoded audio stream St31, and the systemstream encoding parameter data St33. Note that the system encoder 900 isa multiplexer that multiplexes the time-delayed streams St27, St29, andSt31 based on the stream encoding data St33 (timing signal) to generatetitle editing units (VOBs) St35.

The VOB buffer 1000 temporarily stores the video objects VOBs producedby the system encoder 900. The formatter 1100 reads the delayed videoobjects VOB from the VOB buffer 1000 based on the title sequence controlsignal St39 to generate one video zone VZ, and adds the volume filestructure VFS to generate the edited multimedia stream data St43.

The multimedia bitstream MBS St43 edited according to the user-definedscenario is then sent to the recorder 1200. The recorder 1200 processesthe edited multimedia stream date St43 to the data stream St45 format ofthe recording medium M, and thus records the formatted data stream St45to the recording medium M.

DVD Decoder

A preferred embodiment of a digital video disk system authoring decoderDCD in which the multimedia bitstream authoring system of the presentinvention is applied to a digital video disk system is described belowand shown in FIG. 26. The authoring decoder DCD applied to the digitalvideo disk system, referred to below as a DVD decoder DCD, decodes themultimedia bitstream MBS edited using the DVD encoder ECD of the presentinvention, and recreates the content of each title according to theuser-defined scenario. It will also be obvious that the multimediabitstream St45 encoded by this DVD encoder ECD is recorded to a digitalvideo disk medium M.

The basic configuration of the DVD decoder DCD according to thisembodiment is the same as that of the authoring decoder DC shown in FIG.3. The differences are that a different video decoder 3801 (shown as3800 in FIG. 23) is used in place of the video decoder 3800, and areordering buffer 3300 and selector 3400 are disposed between the videodecoder 3801 and synthesizer 3500.

Note that the selector 3400 is connected to the synchronizer 2900, andis controlled by a switching signal St103.

The operation of this DVD decoder DCD is therefore described bellow incomparison with the authoring decoder DC described above.

As shown in FIG. 26, the DVD decoder DCD comprises a multimediabitstream producer 2000, scenario selector 2100, decoding systemcontroller 2300, stream buffer 2400, system deacoder 2500, video buffer2600, sub-picture buffer 2700, audio buffer 2800, synchronizer 2900,video decoder 3801, reordering buffer 3300, sub-picture decoder 3100,audio decoder 3200, selector 3400, synthesizer 3500, video data outputterminal 3600, and audio data output terminal 3700.

The bitstream producer 2000 comprises a recording media drive unit 2004for driving the recording medium M; a reading head 2006 for reading theinformation recorded to the recording medium M and producing the binaryread signal St57; a signal processor 2008 for variously processing theread signal St57 to generate the reproduced bitstream St61; and areproduction controller 2002.

The reproduction controller 2002 is connected to the decoding systemcontroller 2300 from which the multimedia bitstream reproduction controlsignal St53 is supplied, and in turn generates the reproduction controlsignals St55 and St5S) respectively controlling the recording mediadrive unit (motor) 2004 and signal processor 2008.

So that the user-defined video, sub-picture, and audio portions of themultimedia title edited by the authoring encoder EC are reproduced, theauthoring decoder DC comprises a scenario selector 2100 for selectingand reproducing the corresponding scenes (titles). The scenario selector2100 then outputs the selected titles as scenario data to the EVDdecoder DCD.

The scenario selector 2100 preferably comprises a keyboard, CPU, andmonitor. Using the keyboard, the user then inputs the desired scenariobased on the content of the scenario input by the DVD encoder ECD. Basedon the keyboard input, the CEU generates the scenario selection dataSt51 specifying the selected scenario. The scenario selector 2100 isconnected to the decoding system controller 2300 by an infraredcommunications device, for example, and inputs the generated scenarioselection data St51 to the decoding system controller 2300.

The stream buffer 2400 has a specific buffer capacity used totemporarily store the reproduced bitstream St61 input from the bitstreamproducer 2000, extract the volume file structure VFS, the initialsynchronization data SCR (system clock reference) in each pack, and theVOBU control information (DSI) in the navigation pack NV, to generatethe bitstream control data St63. The stream buffer 2400 is alsoconnected to the decoding system controller 2300, to which it suppliesthe generated bitstream control data St63.

Based on the scenario selection data St51 supplied by the scenarioselector 2100, the decoding system controller 2300 then generates thebitstream reproduction control signal St53 controlling the operation ofthe bitstream producer 2000. The decoding system controller 2300 alsoextracts the user-defined playback instruction data from the bitstreamreproduction control signal St53, and generates the decoding informationtable required for decoding control. This decoding information table isdescribed further below with reference to FIGS. 26 and 32. The decodingsystem controller 2300 also extracts the title information recorded tothe optical disk M from the file data structure area FDS of thebitstream control data St63 to generate the title information signalSt200. Note that the extracted title information includes the videomanager VMG, VTS information VTSI, the PGC information entries C₋₋ PBI#j, and the cell presentation time C₋₋ PBTM.

Note that the bitstream control data St63 is generated in pack units asshown in FIG. 19, and is supplied from the stream buffer 2400 to thedecoding system controller 2300, to which the stream buffer 2400 isconnected.

The synchronizer 2900 is connected to the decoding system controller2300 from which it receives the system clock references SCR contained inthe synchronization control data St81 to set the internal system clockSTC and supply the reset system clock St79 to the decoding systemcontroller 2300.

Based on this system clock St79, the decoding system controller 2300also generates the stream read signal St65 at a specific interval andoutputs the read signal St65 to the stream buffer 2400. Note that theread unit in this case is the pack.

The method of generating the stream read signal St65 is described next.

The decoding system controller 2300 compares the system clock reference.SCR contained in the stream control data extracted from the streambuffer 2400 with the system clock St79 supplied from the synchronizer2900, and generates the read request signal St65 when the system clockSt79 is greater than the system clock reference SCR of the bitstreamcontrol data St63. Pack transfers are controlled by executing thiscontrol process on a pack unit.

Based on the scenario selection data St51, the decoding systemcontroller 2300 generates the decoding signal St69 defining the streamIds for the video, sub-picture, and audio bitstreams corresponding tothe selected scenario, and outputs to the system decoder 2500.

When a title contains plural audio tracks, e.g. audio tracks inJapanese, English, French, and/or other languages, and pluralsub-picture tracks for subtitles in Japanese, English, French, and/orother languages, for example, a discrete ID is assigned to each of thelanguage tracks. As described above with reference to FIG. 19, a streamID is assigned to the video data and MPEG audio data, and a substream IDis assigned to the sub-picture data, AC-3 audio-data, linear PCM data,and navigation pack NV information. While the user need never be awareof these ID numbers, the user can select the language of the audioand/or subtitles using the scenario selector 2100. If English languageaudio is selected, for example, the ID corresponding to the Englishaudio track is sent to the decoding system controller 2300 as scenarioselection data St51. The decoding system controller 2300 then adds thisID to the decoding signal St69 output to the system decoder 2500.

Based on the instructions contained in the decoding signal St69, thesystem decoder 2500 respectively outputs the video, sub-picture, andaudio bitstreams input from the stream buffer 2400 to the video buffer2600, sub-picture buffer 2700, and audio buffer 2800 as the encodedvideo stream St71, encoded sub-picture stream st73, and encoded audiostream St75. Thus, when the stream ID input from the scenario selector2100 and the pack ID input from the stream buffer 2400 match, the systemdecoder 2500 outputs the corresponding packs to the respective buffers(i.e., the video buffer 2600, sub-picture buffer 2700, and audio buffer2800).

The system decoder 2500 detects the presentation time stamp PTS anddecoding time stamp DTS of-the smallest control unit in each bitstreamSt67 to generate the time information signal St77. This time informationsignal St77 is supplied to the synchronizer 2900 through the decodingsystem controller 2300 as the synchronization control data St81.

Based on this synchronization control data St81, the synchronizer 2900determines the decoding start timing whereby each of the bitstreams willbe arranged in the correct sequence after decoding, and then generatesand inputs the video stream decoding start signal St89 to the videodecoder 3801 based on this decoding timing. The synchronizer 2900 alsogenerates and supplies the sub-picture decoding start signal St91 andaudio stream decoding start signal St93 to the sub-picture decoder 3100and audio decoder 3200, respectively.

The video decoder 3801 generates the video output request signal St84based on the video stream decoding start signal St89, and outputs to thevideo buffer 2600. In response to the video output request signal St84,the video buffer 2600 outputs the video stream St83 to the video decoder3801. The video decoder 3801 thus detects the presentation timeinformation contained in the video stream St83, and disables the videooutput request signal St84 when the length of the received video streamSt83 is equivalent to the specified presentation time. A video streamequal in length to the specified presentation time is thus decoded bythe video decoder 3801, which outputs the reproduced video signal St95to the reordering buffer 3300 and selector 3400.

Because the encoded video stream is coded using the interframecorrelations between pictures, the coded order and display order do notnecessarily match on a frame unit basis. The video cannot, therefore, bedisplayed in the decoded order. The decoded frames are thereforetemporarily stored to the reordering buffer 3300. The synchronizer 2900therefore controls the switching signal St103 so that the reproducedvideo signal St95 output from the video decoder 3800 and the reorderingbuffer output St97 are appropriately selected and output in the displayorder to the synthesizer 3500.

The sub-picture decoder 3100 similarly generates the sub-picture outputrequest signal St86 based on the sub-picture decoding start signal St91,and outputs to the sub-picture buffer 2700. In response to thesub-picture output request signal St86, the sub-picture buffer 2700outputs the sub-picture stream St85 to the sub-picture decoder 3100.Based on the presentation time information contained in the sub-picturestream St85, the sub-picture decoder 3100 decodes a length of thesub-picture stream St85 corresponding to the specified presentation timeto reproduce and supply to the synthesizer 3500 the sub-picture signalSt99.

The synthesizer 3500 superimposes the selector 3400 output with thesub-picture signal St99 to generate and output the video signal St105 tothe video data output terminal 3600.

The audio decoder 3200 generates and supplies to the audio buffer 2800the audio output request signal St88 based on the audio stream decodingstart signal St93. The audio buffer 2800 thus outputs the audio streamSt87 to the audio decoder 3200. The audio decoder 3200 decodes a lengthof the audio stream St87 corresponding to the specified presentationtime based on the presentation time information contained in the audiostream St87, and outputs the decoded audio stream St101 to the audiodata output terminal 3700.

It is thus possible to reproduce a user-defined multimedia bitstream MBSin real-time according to a user-defined scenario. More specifically,each time the user selects a different scenario, the DVD decoder DCD isable to reproduce the title content desired by the user in the desiredsequence by reproducing the multimedia bitstream MBS corresponding tothe selected scenario.

It should be noted that the decoding system controller 2300 may supplythe title information signal St200 to the scenario selector 2100 bymeans of the infrared communications device mentioned above or anothermeans. Interactive scenario selection controlled by the user can also bemade possible by the scenario selector 2100 extracting the titleinformation recorded to the optical disk M from the file data structurearea FDS of the bitstream control data St63 contained in the titleinformation signal St200, and displaying this title information on adisplay for user selection.

Note, further, that the stream buffer 2400, video buffer 2600,sub-picture buffer 2700, audio buffer 2800, and reordering buffer 3300are expressed above and in the figures as separate entities because theyare functionally different. It will be obvious, however, that a singlebuffer memory can be controlled to provide the same discretefunctionality by time-share controlled use of a buffer memory with anoperating speed plural times faster than the read and write rates ofthese separate buffers.

Multi-scene Control

The concept of multiple angle scene control according to the presentinvention is described below with reference to FIG. 21. As describedabove, titles that can be played back with numerous variations areconstructed from basic scene periods containing data common to eachtitle, and multi-scene periods comprising groups of different scenescorresponding to the various scenario requests. In FIG. 21, scenes 1, 5,and 8 are the common scenes of the basic scene periods. The multi-anglescenes (angles 1, 2, and 3) between scenes 1 and 5, and the parentallocked scenes (scenes 6 and 7) between scenes 5 and 8, are themulti-scene periods.

Scenes taken from different angles, i.e., angles 1, 2, and 3 in thisexample, can be dynamically selected and reproduced during playback inthe multi-angle scene period. In the parental locked scene period,however, only one of the available scenes, scenes 6 and 7, havingdifferent content can be selected, and must be selected staticallybefore playback begins.

Which of these scenes from the multi-scene periods is to be selected andreproduced is defined by the user operating the scenario selector 2100and thereby generating the scenario selection data St51. In scenario 1in FIG. 21 the user (an freely select any of the multi-angle scenes, andscene 6 has been preselected for output in the parental locked sceneperiod. Similarly in scenario 2, the user can freely select any of themulti-angle scenes, and scene 7 has been preselected for output in theparental locked scene period.

With reference to FIGS. 30 and 31, furthermore, the contents of theprogram chain information VTS₋₋ PGCI is described. In FIG. 30, the casethat a scenario requested by the user is shown with respect to a VTSIdata construction. The scenario 1 and scenario 2 shown in FIG. 21 aredescribed as program chain information VTS₋₋ PGC#1 and VTS₋₋ PGC#2.VTS₋₋ PGC#1 describing the scenario 1 consists of cell playbackinformation C₋₋ PBI#1 corresponding to scene 1, C₋₋ PBI#2, C₋₋ PBI#3,and C₋₋ PBI#4 within a multi angle cell block, C₋₋ PBI#5 correspondingto scene 5, C-PBI#6 corresponding to scene 6, and C₋₋ PBI#7corresponding to scene 8.

VTS₋₋ PGCI#2 describing the scenario 2 consists of cell playbackinformation C₋₋ PBI#1 corresponding to scene 1, C-PBI#2, C₋₋ PBI#3, and.C₋₋ PBI#4 within a multi-angle cell block corresponding to a multi-anglescene, C₋₋ PBI#5 corresponding to scene 5, C₋₋ PBI#6 corresponding toscene 7, and C₋₋ PBI#7 corresponding to scene 8. According to thedigital video system data structure, a scene which is a control unit ofa scenario is described as a cell which is a unit thereunder, thus ascenario requested by a user can be obtained.

In FIG. 31, the case that a scenario requested by the user shown in FIG.21 is shown with respect to a VOB data construction VTSTT₋₋ VOBS. Asspecifically shown in FIG. 31, the two scenarios 1 and 2 use the sameVOB data in common. With respect to a single scene commonly owned byeach scenario, VOB#1 corresponding to scene 1, VOB#5 corresponding toscene 5, and VOB#8 corresponding to scene 8 are arranged innon-interleaved block which is the contiguous block.

With respect to the multi-angle data commonly owned by scenarios 1 and2, one angle scene data is constructed by a single VOB. Specificallyspeaking, angle 1 is constructed by VDB#2, and angle 2 is constructed byVOB#3, angle 3 is constructed by VOB#4. Thus constructed multi-angledata is formed as the interleaved block for the sake of switchingbetween each angle and seamless reproduction of each angle data. Scenes6 and 7 peculiar to scenarios 1 and 2, respectively, are formed as theinterleaved block for the sake of seamless reproduction between commonscenes before and behind thereof as well as seamless reproductionbetween each scene.

As described in the above, the user's requesting scenario shown in FIG.21 can be realized by utilizing the video title playback controlinformation shown in FIG. 30 and the title playback VOB data structureshown in FIG. 31.

Seamless Playback

The seamless playback capability briefly mentioned above with regard tothe digital video disk system data structure is described below. Notethat seamless playback refers to the reproduction in a digital videodisk system of multimedia data including video, audio, and sub-picturedata without intermittent breaks in the data or information betweenbasic scene periods, between basic scene periods and multi-sceneperiods, and between multi-scene periods.

Hardware factors contributing to intermittent playback of this data andtitle content include decoder underflow, i.e., an imbalance between thesource data input speed and the decoding speed of the input source data.

Other factors relate to the properties of the playback data. When theplayback data is data that must be continuously reproduced for aconstant time unit in order for the user to understand the content orinformation, e.g., audio data, data continuity is lost when the requiredcontinuous presentation time cannot be assured. Reproduction of suchinformation whereby the required continuity is assured is referred to as"contiguous information reproduction," or "seamless informationreproduction." Reproduction of this information when the requiredcontinuity cannot be assured is referred to as "non-continuousinformation reproduction," or "non-seamless information reproduction."It is obvious that continuous information reproduction andnon-continuous information reproduction are, respectively, seamless andnon-seamless reproduction.

Note that seamless reproduction can be further categorized as seamlessdata reproduction and seamless information reproduction. Seamless datareproduction is defined as preventing physical blanks or interruptionsin the data playback (intermittent reproduction) as a result of a bufferunderflow state, for example. Seamless information reproduction isdefined as preventing apparent interruptions in the information whenperceived by the user (intermittent presentation) when recognizinginformation from the playback data where there are no actual physicalbreaks in the data reproduction. The specific method enabling seamlessreproduction as thus described is described later below with referenceto FIGS. 23 and 24.

Interleaving

The DVD data system streams described above are recorded using anappropriate authoring encoder EC as a movie or other multimedia title ona DVD recording medium. Note that the following description refers to amovie as the multimedia title being processed, but it will be obviousthat the invention shall not be so limited.

Supplying a single movie in a format enabling the movie to be used inplural different cultural regions or countries requires the script to berecorded in the various languages used in those regions or countries. Itmay even necessitate editing the content to conform to the mores andmoral expectations of different cultures. Even using such alarge-capacity storage system as the DVD system, however, it isnecessary to reduce the bit rate, and therefore the image quality, ifplural full-length titles edited from a single common source title arerecorded to a single disk. This problem can be solved by recording thecommon parts of plural titles only once, and recording the segmentsdifferent in each title for each different title only. This method makesit possible to record plural titles for different countries or culturesto a single optical disk without reducing the bit rate, and, therefore,retaining high image quality.

As shown in FIG. 21, the titles recorded to a single optical diskcontain basic scene periods of scenes common to all scenarios, andmulti-scene periods containing scenes specific to certain scenarios, toprovide parental lock control and multi-angle scene control functions.

In the case of the parental lock control function, titles containing sexscenes, violent scenes, or other scenes deemed unsuitable for children,i.e., so-called "adult scenes," are-recorded with a combination ofcommon scenes, adult scenes, and children's scenes. These title streamsare achieved by arraying the adult and children's scenes to multi-sceneperiods between the common basic scene periods.

Multi-angle control can be achieved in a conventional single-angle titleby recording plural multimedia scenes obtained by recording the subjectsfrom the desired plural camera angles to the multi-scene periods arrayedbetween the common basic scene periods. Note, however, that while theseplural scenes are described here as scenes recorded from differentcamera angles (positions), it will be obvious that the scenes may berecorded from the same camera angle but at different times, datagenerated by computer graphics, or other video data.

When data is shared between different scenarios of a single title, it isobviously necessary to move the laser beam LS from the common scene datato the non-common scene data during reproduction, i.e., to move theoptical pickup to a different position on the DVD recording medium RC1.The problem here is that the time required to move the optical pickupmakes it difficult to continue reproduction without creating breaks inthe audio or video, i.e., to sustain seamless reproduction. This problemcan be theoretically solved by providing a track buffer (stream buffer2400) to delay data output an amount equivalent to the worst accesstime. In general, data recorded to an optical disk is read by theoptical pickup, appropriately processed, and temporarily stored to thetrack buffer. The stored data is subsequently decoded and reproduced asvideo or audio data.

To thus enable the user to selectively excise scenes and choose fromamong plural scenes, a state wherein non-selected scene data is recordedinserted between common scene data and selective scene data necessarilyoccurs because the data units associated with individual scenes arecontiguously recorded to the recording tracks of the recording medium.If data is then read in the recorded sequence, non-select(ed scene datamust be accessed before accessing and decoding the selected scene data,and seamless connections with the selected scene is difficult. Theexcellent random access characteristics of the digital video disksystem, however, make seamless connections with the selected scenespossible.

In other wards, by splitting scene-specific data into plural units of aspecified data size, and interleaving plural split data units fordifferent scenes in a predefined sequence that is recorded to the diskwithin the jumping range whereby a data underflow state does not occur,it is possible to reproduce the selected scenes without datainterruptions by intermittently accessing and decoding the data specificto the selected scenes using these split data units. Seamless datareproduction is thereby assured.

Interleaved Block and Interleave Unit

The interleaving method enabling seamless data reproduction according tothe present invention is described below with reference to FIG. 24 andFIG. 71. Shown in FIG. 24 is a case-from which three scenarios may bederived, i.e., branching from one video object VOB-A to one of pluralvideo objects VOB-B, VOB-C, and VOB-D, and then merging back again to asingle video object VOB-E. The actual arrangement of these blocksrecorded to a data recording track TR on disk is shown in FIG. 71.

Referring to FIG. 71, VOB-A and VOB-E are video objects with independentplayback start and end times, and are in principle arrayed to contiguousblock regions. As shown in FIG. 24, the playback start and end times ofVOB-B, VOB-C, and VOB-D are aligned during interleaving. The interleaveddata blocks are then recorded to the disk to a contiguous interleavedblock region. The contiguous block regions and interleaved block regionsare then written to disk in the track path Dr direction in the playbacksequence. Plural video objects VOB, i.e., interleaved video objectsVOBS, arrayed to the data recording track TR are shown in FIG. 71.

Referring to FIG. 72, data regions to which data is continuously arrayedare called "blocks," of which there are two types: "contiguous blockregions" in which VOB with discrete starting and end points arecontiguously arrayed, and "interleaved block regions" in which pluralVOB with aligned starting and end points are interleaved. The respectiveblocks are arrayed as shown in FIG. 74 in the playback sequence, i.e.,block 1, block 2, block 3, . . . block 7.

As shown in FIG. 72, the VTS title VOBS (VTSTT₋₋ VOBS) consist of blocks1-7, inclusive. Block 1 contains VOB 1 alone. Blocks 2, 3, 5, and 7similarly discretely contain VOBS 2, 3, 6, and 10. Blocks 2, 3, 5, and 7are thus contiguous block regions.

Block 4, however, contains VOB 4 and VOB 5 interleaved together, whileblock 6 contains VOB 7, VOB 8, and VOB 9 interleaved together. Blocks 4and 6 are thus interleaved block regions.

The internal data structure of the contiguous block regions is shown inFIG. 73 with VOB-i and VOB-j arrayed as the contiguous blocks in theVOBs. As described with reference to FIG. 16, VOB-i and VOB-j inside thecontiguous block regions are further logically divided into cells as theplayback unit. Both VOB-i and VoB-j in this figure are shown comprisingthree cells CELL #1, CELL #2, and CELL #3.

Each cell comprises one or more video object unit VOBU with the videoobject unit VOBU defining the boundaries of the cell. Each cell alsocontains information identifying the position of the cell in the programchain PGC (the playback control information of the digital video disksystem). More specifically, this position information is the address ofthe first and last VOBU in the cell. As also shown in FIG. 73, these VOBand the cells defined therein are also recorded to a contiguous blockregion so that contiguous blocks are contiguously reproduced.Reproducing these contiguous blocks is therefore not a problem.

The internal data structure of the interleaved block regions is shown inFIG. 74. In the interleaved block regions each video-object VOB isdivided into interleaved units ILVU, and the interleaved units ILVUassociated with each VOB are alternately arrayed. Cell boundaries aredefined independently of the interleaved units ILVU. For example, VOB-kis divided into four interleaved units ILVUk1, ILVUk2, ILVUk3, andILVUk4, and are confined by a single cell CELL#k. VOB-k is likewisedivided into four interleaved units ILVUm1, ILVUm2, ILVUm3, and ILVUm4,and is confined by a single cell CELL#m. Note that instead of a singlecell CELL#k or CELL#m, each of VOB-k and VOB-m can be divided into morethan two cells. The interleaved units ILVU thus contains both audio andvideo data.

In the example shown in FIG. 74, the interleaved units ILVUk1, ILVUk2,ILVUk3, and ILVUk4, and ILVUm1, ILVUm2, ILVUm3, and ILVUm4, from twodifferent video objects VOB-k and VOB-m are alternately arrayed within asingle interleaved block. By interleaving the interleaved units ILVU oftwo video objects VOB in this sequence, it is possible to achieveseamless reproduction branching from one scene to one of plural scenes,and from one of plural scenes to one scene.

Multi-scene Control

The multi-scene period is described together with the concept ofmultiscene control according to the present invention using, by way ofexample, a title comprising scenes recorded from different angles.

Each scene in multi-scene control is recorded from the same angle, butmay be recorded at different times or may even be computer graphicsdata. The multi-angle scene periods may therefore also be calledmulti-scene periods.

Parental Control

The concept of recording plural titles comprising alternative scenes forsuch functions as parental lock control and recording director's cuts isdescribed below using FIG. 15.

An example of a multi-rated title stream providing for parental lockcontrol is shown in FIG. 15. When so-called "adult scenes" containingsex, violence, or other scenes deemed unsuitable for children arecontained in a title implementing parental lock control, the titlestream is recorded with a combination of common system streams SSa, SSb,and Sse, an adult-oriented system stream SSc containing the adultscenes, and a child-oriented system stream SSd containing only thescenes suitable for children. Title streams such as this are recorded asa multi-scene system stream containing the adult-oriented system streamSsc and the child-oriented system stream Ssd arrayed to the multi-sceneperiod between common system streams Ssb and Sse.

The relationship between each of the component titles and the systemstream recorded to the program chain PGC of a title stream thuscomprised is described below.

The adult-oriented title program chain PGC1 comprises in sequence thecommon system streams Ssa and Ssb, the adult-oriented system stream Ssc,and the common system stream Sse. The child-oriented title program chainPGC2 comprises in sequence the common system streams Ssa and Ssb, thechild-oriented system stream Ssd, and the common system stream Sse.

By thus arraying the adult-oriented system stream Ssc and child-orientedsystem stream Ssd to a multi-scene period, the decoding methodpreviously described can reproduce the title containing adult-orientedcontent by reproducing the common system streams Ssa and Ssb, thenselecting and reproducing the adult-oriented system stream Ssc, and thenreproducing the common system stream Sse as instructed by theadult-oriented title program chain PGC1. By alternatively following thechild-oriented title program chain PGC2 and selecting the child-orientedsystem stream Ssd in the multi-scene period, a child-oriented title fromwhich the adult-oriented scenes have been expurgated can be reproduced.

This method of providing in the title stream a multi-scene periodcontaining plural alternative scenes, selecting which of the scenes inthe multi-scene period are to be reproduced before playback begins, andgenerating plural titles containing essentially the same title contentbut different scenes in part, is called parental lock control.

Note that parental lock control is so named because of the perceivedneed to protect children from undesirable content. From the perspectiveof system stream processing, however, parental lock control is atechnology for statically generating different title streams by means ofthe user pre-selecting specific scenes from a multi-scene period. Note,further, that this contrasts with multi-angle scene control, which is atechnology for dynamically changing the content of a single title bymeans of the user selecting scenes from the multi-scene period freelyand in real-time during title playback.

This parental lock control technology can also be used to enable titlestream editing such as when making the director's cut. The director'scut refers to the process of editing certain scenes from a movie to, forexample, shorten the total presentation time. This may be necessary, forexample, to edit a feature-length movie for viewing on an airplane wherethe presentation time is too long for viewing within the flight time orcertain content may not be acceptable. The movie director thusdetermines which scenes may be cut to shorten the movie. The title canthen be recorded with both a full-length, unedited system stream and anedited system stream in which the edited scenes are recorded tomulti-scene periods. At the transition from one system stream to anothersystem stream in such applications, parental lock control must be ableto maintain smooth playback image output. More specifically, seamlessdata reproduction whereby a data underflow state does not occur in theaudio, video, or other buffers, and seamless information reproductionwhereby no unnatural interruptions are audibly or visibly perceived inthe audio and video playback, are necessary.

Multi-angle Control

The concept of multi-angle scene control in the present invention isdescribed next with reference to FIG. 33. In general, multimedia titlesare obtained by recording both the audio and video information(collectively "recording" below) of the subject over time T. The angledscene blocks #SC1, #SM1, #SM2, #SM3, and #SC3 represent the multimediascenes obtained at recording unit times T1, T2, and T3 by recording thesubject at respective camera angles. Scenes #SM1, #SM2, and #SM3 arerecorded at mutually different (first, second, and third) camera anglesduring recording unit time T2, and are referenced below as the first,second, and third angled scenes.

Note that the multi-scene periods referenced herein are basicallyassumed to comprise scenes recorded from different angles. The scenesmay, however, be recorded from the same angle but at different times, orthey may be computer graphics data. The multi-angle scene periods arethus the multi-scene periods from which plural scenes can be selectedfor presentation in the same time period, whether or rot the scenes areactually recorded at different camera angles.

Scenes #SC1 and #SC3 are scenes recorded at the same common camera angleduring recording unit times T1 and T3, i.e., before and after themulti-angle scenes. These scenes are therefore called "common anglescenes." Note that one of the multiple camera angles used in themulti-angle scenes is usually the same as the common camera angle.

To understand the relationship between these various angled scenes,multi-angle scene control is described below using a live broadcast of abaseball game for example only.

The common angle scenes #SC1 and #SC3 are recorded at the common cameraangle, which is here defined as the view from center field on the axisthrough the pitcher, batter, and catcher.

The first angled scene #SM1 is recorded at the first multi-camera angle,i.e., the camera angle from the backstop on the axis through thecatcher, pitcher, and batter. The second angled scene #SM2 is recordedat the second multi-camera angle, i.e., the view from center field onthe axis through the pitcher, batter, and catcher. Note that the secondangled scene #SM2 is thus the same as the common camera angle in thisexample. It therefore follows that the second angled scene #SM2 is thesame as the common angle scene #SC2 recorded during recording unit timeT2. The third angled scene #SM3 is recorded at the third multi-cameraangle, i.e., the camera angle from the backstop focusing on the infield.

The presentation times of the multiple angle scenes #SM1, #SM2, and #SM3overlap in recording unit time T2; this period is called the"multi-angle scene period." By freely selecting one of the multipleangle scenes #SM1, #SM2, and #SM3 in this multi-angle scene period, theviewer is able to change his or her virtual viewing position to enjoy adifferent view of the game as though the actual camera angle is changed.Note that while there appears to be a time gap between common anglescenes #SC1 and #SC3 and the multiple angle scenes #SM1, #SM2, and #SM3in FIG. 33, this is simply to facilitate the use of arrows in the figurefor easier description of the data reproduction paths reproduced byselecting different angled scenes. There is no actual time gap duringplayback.

Multi-angle scene control of the system stream based on the presentinvention is described next with reference to FIG. 23 from theperspective of connecting data blocks. The multimedia data correspondingto common angle scene #SC is referenced as common angle data BA, and thecommon angle data BA in recording unit times T1 and T3 are referenced asBA1 and BA3, respectively. The multimedia data corresponding to themultiple angle scenes #SM1, #SM2, and #SM3 are referenced as first,second, and third angle scene data MA1, MA2, and MA3. As previouslydescribed with reference to FIG. 33, scenes from the desired angled canbe viewed by selecting one of the multiple angle data units MA1, MA2,and MA3. There is also no time gap between the common angle data BA1 andBA3 and the multiple angle data units MA1, MA2, and MA3.

In the case of an MPEG system stream, however, intermittent breaks inthe playback information can result between the reproduced common andmultiple angle data units depending upon the content of the data at theconnection between the selected multiple angle data unit MA1, MA2, andMA3 and the common angle data BA (either the first common angle data BA1before the angle selected in the multi-angle scene period or the commonangle data BA3 following the angle selected in the multi-angle sceneperiod). The result in this case is that the title stream is notnaturally reproduced as a single contiguous title, i.e., seamless datareproduction is achieved but non-seamless information reproductionresults.

The multi-angle selection process whereby one of plural scenes isselectively reproduced from the multi-angle scene period with seamlessinformation presentation to the scenes before and after is describedbelow with application in a digital video disk system using FIG. 23.

Changing the scene angle, i.e., selecting one of the multiple angle dataunits MA1, MA2, and MA3, must be completed before reproduction of thepreceding common angle data BA1 is completed. It is extremely difficult,for example, to change to a different angle data unit MA2 duringreproduction of common angle data BA1. This is because the multimediadata has a variable length coded MPEG data structure, which makes itdifficult to find the data break points (boundaries) in the selecteddata blocks. The video may also he disrupted when the angle is changedbecause inter-frame correlations are used in the coding process. Thegroup₋₋ of₋₋ pictures GOP processing unit of the MPEG standard containsat least one refresh frame, and closed processing not referencing framesbelonging to another GOP is possibLe within this GOP processing unit.

In other words, if the desired angle data, e. g., MA3, is selectedbefore reproduction reaches the multi-angle scene period, and at thelatest by the time reproduction of the preceding common angle data BA1is completed, the angle data selected from within the multi-angle sceneperiod can be seamlessly reproduced. However, it is extremely difficultwhile reproducing one angle to select and seamlessly reproduce anotherangle within the same multi-angle scene period. It is thereforedifficult when in a multi-angle scene period to dynamically select adifferent angle unit presenting, for example, a view from a differentcamera angle.

Flow Chart: Encoder

The encoding information table generated by the encoding systemcontroller 200 from information extracted from the scenario data St7 isdescribed below referring to FIG. 27.

The encoding information table contains VOB set data streams containingplural VOB corresponding to the scene periods beginning and ending atthe scene branching and connecting points, and VOB data streamscorresponding to each scene. These VOB set data streams shown in FIG. 27are the encoding information tables generated at step #100 in FIG. 34 bythe encoding system controller 200 for creating the DVD multimediastream based on the user-defined title content.

The user-defined scenario contains branching points from common scenesto plural scenes, or connection points to other common scenes. The VOBcorresponding to the scene period delimited by these branching andconnecting points is a VOB set, and the data generated to encode a VOBset is the VOB set data stream. The title number specified by the VOBset data stream is the title number TITLE₋₋ NO of the VOB set datastream.

The VOB Set data structure in FIG. 27 shows the data content forencoding one VOB set in the VOB set data stream, and comprises: the VOBset number VOBS₋₋ NO, the VOB number VOB₋₋ NO in the VOB set, thepreceding VOB seamless connection flag VOB₋₋ Fsb, the following VOBseamless connection flag VOB₋₋ Fsf, the multi-scene flag VOB₋₋ Fp, theinterleave flag VOB₋₋ Fi, the multi-angle flag VOB₋₋ Fm, the multi-angleseamless switching flag VOB₋₋ FsV, the maximum bit rate of theinterleaved VOB ILV₋₋ BR, the number of interleaved VOB divisions ILV₋₋DIV, and the minimum interleaved unit presentation time ILVU₋₋ MT.

The VOB set number VOBS₋₋ NO is a sequential number identifying the VOBset and the position of the VOB set in the reproduction sequence of thetitle scenario.

The VOB number VOB₋₋ NO is a sequential number identifying the VOB andthe position of the VOB in the reproduction sequence of the titlescenario.

The preceding VOB seamless connection flag VOB₋₋ Fsb indicates whether aseamless connection with the preceding VOB is required for scenarioreproduction.

The following VOB seamless connection flag VOB₋₋ Fsf indicates whetherthere is a seamless connection with the following VOB during scenarioreproduction.

The multi-scene flag VOB₋₋ Fp identifies whether the VOB set comprisesplural video objects VOB.

The interleave flag VOB₋₋ Fi identifies whether the VOB in the VOB setare interleaved.

The multi-angle flag VOB₋₋ Fm identifies whether the VOB set is amulti-angle set.

The multi-angle seamless switching flag VOB₋₋ FsV identifies whetherangle changes within the multi-angle scene period are seamless or not.

The maximum bit rate of the interleaved VOB ILV₋₋ BR defines the maximumbit rate of the interleaved VOBs.

The number of interleaved VOB divisions ILV₋₋ DIV identifies the numberof interleave units in the interleaved VOB.

The minimum interleave unit presentation time ILVU₋₋ MT defines the timethat can be reproduced when the bit rate of the smallest interleave unitat which a track buffer data underflow state does not occur is themaximum bit rate of the interleaved VOB ILV₋₋ BR during interleavedblock reproduction.

The encoding information table for each VOB generated by the encodingsystem controller 200 based on the scenario data St7 is described belowreferring to FIG. 28. The VOB encoding parameters described below andsupplied to the video encoder 300, audio encoder 700, and system encoder900 for stream encoding are produced based on this encoding informationtable.

The VOB data streams shown in FIG. 28 are the encoding informationtables generated at step #100 in FIG. 34 by the encodingsystem-controller 200 for creating the DVD multimedia stream based-onthe user-defined title content.

The encoding unit is the video object VOB, and the data generated toencode each video object VOB is the VOB data stream. For example, a VOBset comprising three angle scenes comprises three video objects VOB. Thedata structure shown in FIG. 28 shows the content of the data forencoding one VOB in the VOB data stream.

The VOB data structure contains the video material start time VOB₋₋ VST,the video material end time VOB₋₋ VEND, the video signal type VOB₋₋ V₋₋KIND, the video encoding bit rate V₋₋ BR, the audio material start timeVOB₋₋ AST, the audio material end time VOB₋₋ AEND, the audio codingmethod VOB₋₋ A₋₋ KIND, and the audio encoding bit rate A₋₋ BR.

The video material start time VOB₋₋ VST is the video encoding start timecorresponding to the time of the video signal.

The video material end time VOB₋₋ VEND is the video encoding end timecorresponding to the time of the video signal.

The video material type VOB₋₋ V₋₋ KIND identifies whether the encodedmaterial is in the NTSC or PAL format, for example, or is photographicmaterial (a movie, for example) converted to a television broadcastformat (so-called telecine conversion).

The video encoding bit rate V₋₋ BR is the bit rate at which the videosignal is encoded.

The audio material start time VOB₋₋ AST is the audio encoding start timecorresponding to the time of the audio signal.

The audio material end time VOB₋₋ AEND is the audio encoding end timecorresponding to the time of the audio signal.

The audio coding method VOB₋₋ A₋₋ KIND identifies the audio encodingmethod as AC-3, MPEG, or linear PCM, for example.

The audio encoding bit rate A₋₋ BR is the bit rate at which the audiosignal is encoded.

The encoding parameters used by the video encoder 300, sub-pictureencoder 500, and audio encoder 700, and system encoder 900 for VOBencoding are shown in FIG. 29. The encoding parameters include: the VOBnumber VOB₋₋ NO, video encode start time V₋₋ STTM, video encode end timeV₋₋ ENDTM, the video encode mode V₋₋ ENCMD, the video encode bit rateV₋₋ RATE, the maximum video encode bit rate V₋₋ MRATE, the GOP structurefixing flag GOP₋₋ Fxflag, the video encode GOP structure GOPST, theinitial video encode data V₋₋ INTST, the last video encode data V₋₋ENDST, the audio encode start time A₋₋ STTM, the audio encode end timeA₋₋ ENDTM, the audio encode bit rate A₋₋ RATE, the audio encode methodA₋₋ ENCMD, the audio start gap A₋₋ STGAP, the audio end gap A₋₋ ENDGAP,the preceding VOB number B₋₋ VOB₋₋ NO, and the following VOB number F₋₋VOB₋₋ NO.

The VOB number VOB₋₋ NO is a sequential number identifying the VOB andthe position of the VOB in the reproduction sequence of the titlescenario.

The video encode start time V₋₋ STTM is the start time of video materialencoding.

The video encode end time V₋₋ ENDTM is the end time of video materialencoding.

The video encode mode V₋₋ ENCMD is an encoding mode for declaringwhether reverse telecine conversion shall be accomplished during videoencoding to enable efficient coding when the video material is telecineconverted material.

The video encode bit rate V₋₋ RATE is the average bit rate of videoencoding.

The maximum video encode bit rate V₋₋ MRATE is the maximum bit rate ofvideo encoding.

The GOP structure fixing flag GOP₋₋ Fxflag specifies whether encoding isaccomplished without changing the GOP structure in the middle of thevideo encoding process. This is a useful parameter for declaring whetherseamless switch is enabled in a multi-angle scene period.

The video encode GOP structure GOPST is the GOP structure data fromencoding.

The initial video encode data V₋₋ INTST sets the initial value of theVBV buffer (decoder buffer) at the start of video encoding, and isreferenced during video decoding to initialize the decoding buffer. Thisis a useful parameter for declaring seamless reproduction with thepreceding encoded video stream.

The last video encode data V₋₋ ENDST sets the end value of the VBVbuffer (decoder buffer) at the end of video encoding, and is referencedduring video decoding to initialize the decoding buffer. This is auseful parameter for declaring seamless reproduction with the precedingencoded video stream.

The audio encode start time A₋₋ STTM is the start time of audio materialencoding.

The audio encode end time A₋₋ ENDTM is the end time of audio materialencoding.

The audio encode bit rate A₋₋ RATE is the bit rate used for audioencoding.

The audio encode method A₋₋ ENCMD identifies the audio encoding methodas AC-3, MPEG, or linear PCM, for example.

The audio start gap A₋₋ STGAP is the time offset between the start ofthe audio and video presentation at the beginning of a VOB. This is auseful parameter for declaring seamless reproduction with the precedingencoded system stream.

The audio end gap A₋₋ ENDGAP is the time offset between the end of theaudio and video presentation at the end of a VOB. This is a usefulparameter for declaring seamless reproduction with the preceding encodedsystem stream.

The preceding VOB number B₋₋ VOB₋₋ NO is the VOB₋₋ NO of the precedingVOB when there is a seamlessly connected preceding VOB.

The following VOB number F₋₋ VOB₋₋ NO is the VOB₋₋ NO of the followingVOB when there is a seamlessly connected following VOB.

The operation of a DVD encoder ECD according to the present invention isdescribed below with reference to the flow chart in FIG. 34. Note thatthe steps shown with a double line are subroutines. It should be obviousthat while the operation described below relates specifically in thiscase to the DVD encoder ECD of the present invention, the operationdescribed also applies to an authoring encoder EC.

At step #100, the user inputs the editing commands according to theuser-defined scenario while confirming the content of the multimediasource data e streams St1, St2, and st3.

At step #200, the scenario editor 100 generates the scenario data St7containing the above edit command information according to the user'sediting instructions.

When generating the scenario data St7 in step #200, the user editingcommands related to multi-angle and parental lock multi-scene periods inwhich interleaving is presumed must be input to satisfy the followingconditions.

First, the VOB maximum bit rate must be set to assure sufficient imagequality, and the track buffer capacity, jump performance, jump time, andjump distance of the DVD decoder DCD used as the reproduction apparatusof the DVD encoded data must be determined. Based on these values, thereproduction time of the shortest interleaved unit is obtained fromequations 3 and 4. Based on the reproduction time of each scene in themulti-scene period, it must then be determined whether equations 5 and 6are satisfied. If equations 5 and 6 are not satisfied, the user mustchange the edit commands until equations 5 and 6 are satisfied by, forexample, connecting part of the following scene to each scene in themulti-scene period.

When multi-angle edit commands are used, equation 7 must be satisfiedfor seamless switching, and edit commands matching the audioreproduction time with the reproduction time of each scene in each anglemust be entered. If non-seamless switching is used, the user must entercommands to satisfy equation 8.

At step #300, the encoding system controller 200 first determineswhether the target scene is to be seamlessly connected to the precedingscene based on the scenario data St7.

Note that when the preceding scene period is a multi-scene periodcomprising plural scenes but the presently selected target scene is acommon scene (not in a multi-scene period), a seamless connection refersto seamlessly connecting the target scene with any one of the scenescontained in the preceding multi-scene period. When the target scene isa multi-scene period, a seamless connection still refers to seamlesslyconnecting the target scene with any one of the scenes from the samemulti-scene period.

If step #300 returns NO, i.e., a non-seamless connection is valid, theprocedure moves to step #400.

At step #400, the encoding system controller 200 resets the precedingSOB seamless connection flag VOB₋₋ Fsb indicating whether there is aseamless connection between the target and preceding scenes. Theprocedure then moves to step #600.

On the other hand, if step #300 returns YES, i.e., there is a seamlessconnection to the preceding scene, the procedure moves to step #500.

At step #500 the encoding system controller 200 sets the preceding VOBseamless connection flag VOB₋₋ Fsb. The procedure then moves to step#600.

At step #600 the encoding system controller 200 determines whether thereis a seamless connection between the target and following scenes basedon scenario data st7. If step #600 returns NO, i.e., a non-seamlessconnection is valid, the procedure moves to step #700.

At step #700, the encoding system controller 200 resets the followingVOB seamless connection flag VOB₋₋ Fsf indicating whether there is aseamless connection with the following scene. The procedure then movesto step #900.

However, if step #600 returns YES, i.e., there is a seamless connectionto the following scene, the procedure moves to step #800.

At step #800 the encoding system controller 200 sets the following VOBseamless connection flag VOB₋₋ Fsf. The procedure then moves to step#900.

At step #900 the encoding system controller 200 determines whether thereis more than connection target scene, i.e., whether a multi-scene periodis selected, based on the scenario data St7. As previously described,there are two possible control methods in multi-scene periods: parentallock control whereby only one of plural possible reproduction paths thatcan be constructed from the scenes in the multi-scene period isreproduced, and multi-angle control whereby the reproduction path can beswitched within the multi-scene period to present different viewingangles.

If step #900 returns NO, i.e., there are not multiple scenes, theprocedure moves to step #1000.

At step #1000 the multi-scene flag VOB₋₋ Fp identifying whether the VOBset comprises plural video objects VOB (a multi-scene period isselected) is reset, and the procedure moves to step #1800 for encodeparameter production. This encode parameter production subroutine isdescribed below.

However, if step #900 returns YES, there is a multi-scene connection,the procedure moves to step #1100.

At step #1100, the multi-scene flag VOB₋₋ Fp is set, and the proceduremoves to step #1200 whereat it is judged whether a multi-angleconnection is selected, or not.

At step #1200 it is determined whether a change is made between pluralscenes in the multi-scene period, i.e., whether a multi-angle sceneperiod is selected. If step #1200 returns NO, i.e., no scene change isallowed in the multi-scene period as parental lock control reproducingonly one reproduction path has been selected, the procedure moves tostep #1300.

At step #1300 the multi-angle flag VOB₋₋ Fm identifying whether thetarget connection scene is a multi-angle scene is reset, and theprocedure moves to step #1302.

At step #1302 it is determined whether either the preceding VOB seamlessconnection flag VOB Fsb or following VOB seamless connection flag VOB₋₋Fsf is set. If step #1302 returns YES, i.e., the target connection sceneseamlessly connects to the preceding, the following, or both thepreceding and following scenes, the procedure moves to step #1304.

At step #1304 the interleave flag VOB₋₋ Fi identifying whether the VOB,the encoded data of the target scene, is interleaved is set. Theprocedure then moves to step #1800.

However, if step #1302 returns NO, i.e., the target connection scenedoes not seamlessly connect to the preceding or following scene, theprocedure moves to step #1306.

At step #1306 the interleave flag VOB₋₋ Fi is reset, and the proceduremoves to step #1800.

If step #1200 returns YES, however, i. e., there is a multi-angleconnection, the procedure moves to step #1400.

At step #1400, the multi-angle flag VOB₋₋ Fm and interleave flag VOB₋₋Fi are set, and the procedure moves to step #1500.

At step #1500 the encoding system controller 200 determines whether theaudio and video can be seamlessly switched in a multi-angle sceneperiod, i.e., at a reproduction unit smaller than the VOB, based on thescenario data St7. If step #1500 returns NO, i.e., non-seamlessswitching occurs, the procedure moves to step #1600.

At step #1600 the multi-angle seamless switching flag VOB₋₋ FsVindicating whether angle changes within the multi-angle scene period areseamless or not is reset, and the procedure moves to step #1800.

However, if step #1500 returns YES, i.e., seamless switching occurs, theprocedure moves to step #1700.

At step #1700 the multi-angle seamless switching flag VOB₋₋ FsV is set,and the procedure moves to step #1800.

Therefore, as shown by the flow chart in FIG. 51, encode parameterproduction (step #1800) is only begun after the editing information isdetected from the above flag settings in the scenario data St7reflecting the user-defined editing instructions.

Based on the user-defined editing instructions detected from the aboveflag settings in the scenario data St7, information is added to theencoding information tables for the VOB Set units and VOB units as shownin FIGS. 27 and 28 to encode the source streams, and the encodingparameters of the VOB data units shown in FIG. 29 are produced, in step#1800. The procedure then moves to step #1900 for audio and videoencoding.

The encode parameter production steps (step #1800) are described ingreater detail below referring to FIGS. 35, 36, 37 and 38.

Based on the encode parameters produced in step #1800, the video dataand audio data are encoded in step #1900, and the procedure-moves tostep #2000.

Note that the sub-picture data is normally inserted during videoreproduction on an as-needed basis, and contiguity with the precedingand following scenes is therefore not usually necessary. Moreover, thesub-picture data is normally video information for one frame, and unlikeaudio and video data having an extended time-base, sub-picture data isusually static, and is not normally presented continuously. Because thepresent invention relates specifically to seamless and non-seamlesscontiguous reproduction as described above, description of sub-picturedata encoding is omitted herein for simplicity.

Step #2000 is the last step in a loop comprising steps #300 to step#2000, and causes this loop to be repeated as many tires as there areVOB Sets. This loop formats the program chain VTS₋₋ PGC#i to contain thereproduction sequence and other reproduction information for each VOB inthe title (FIG. 16) in the program chain data structure, interleaves theVOB in the multi-scene periods, and completes the VOB Set data streamand VOB data stream needed for system stream encoding. The procedurethen moves to step #2100.

At step #2100 the VOB Set data stream is completed as the encodinginformation table by adding the total number of VOB Sets VOBS₋₋ NUMobtained as a result of the loop through step #2000 to the VOB Set datastream, and setting the number of titles TITLE₋₋ NO defining the numberof scenario reproduction paths in the scenario data St7. The procedurethen moves-to step #2200.

System stream encoding producing the VOB (VOB#i) data in the VTS titleVOBS (VTSTT₋₋ VOBS) (FIG. 16) is accomplished in step #2200 based on theencoded video stream and encoded audio stream output from step #1900,and the encode parameter, in FIG. 29. The procedure then moves to step#2300.

At step #2300 the VTS information VTSI, VTSI management table VTSI₋₋MAT, VTSPGC information table VTS₋₋ PGCIT, and the program chaininformation VTS₋₋ PGCI#i controlling the VOB data reproduction sequenceshown in FIG. 16 are produced, and formatting to, for example,interleave the VOB contained in the multi-scene periods, isaccomplished. The specific steps executed in this formatting operationare described below with reference to FIGS. 49, 50, 51, 52, and 53.

The encode parameter production subroutine shown as step #1800 in FIG.34B is described next using FIGS. 52, 35, 36, 37, and 38 using by way ofexample the operation generating the encode parameters for multi-anglecontrol.

Starting from FIG. 35, the process for generating the encode parametersof a non-seamless switching stream with multi-angle control is describedfirst. This stream is generated when step #1500 in FIG. 34 returns NOand the following flags are set as shown: VOB₋₋ Fsb=1 or VOB₋₋ Fsf=1,VOB₋₋ Fp=1, VOB₋₋ Fi=1, VOB₋₋ Fm=1, and VOB₋₋ FsV=0. The followingoperation produces the encoding information tables shown in FIG. 27 andFIG. 28, and the encode parameters shown in FIG. 29.

At step #1812, the scenario reproduction sequence (path) contained inthe scenario data St7 is extracted, the VOB Set number VOBS₋₋ NO is set,and the VOB number VOB₋₋ NO is set for one or more VOB in the VOB Set.

At step #1814 the maximum bit rate ILV₋₋ BR of the interleaved VOB isextracted from the scenario data St7, and the maximum video encode bitrate V₋₋ MRATE from the encode parameters is set based on the interleaveflag VOB₋₋ Fi setting (=1).

At step #1816, the minimum interleaved unit presentation time ILVU₋₋ MTis extracted from the scenario data St7.

At step #1818, the video encode GOP structure GOPST values N=15 and M=3are set, and the GOP structure fixing flag GOP₋₋ Fxflag is set (=1),based on the multi-scene flag VOE₋₋ Fp setting (=1).

Step #1820 is the common VOB data setting routine, which is describedbelow referring to the flow chart in FIG. 36. This common VOB datasetting routine produces the encoding information tables shown in FIGS.27 and 28, and the encode parameters shown in FIG. 29.

At step #1822 the video material start time VOB₋₋ VST and video materialend time VOB₋₋ VEND are extracted for each VOB, and the video encodestart time V₋₋ STTM and video encode end time V₋₋ ENDTM are used asvideo encoding parameters.

At step #1824 the audio material start time VOB₋₋ AST of each VOB isextracted from the scenario data St7, and the audio encode start timeA₋₋ STTM is set as an audio encoding parameter.

At step #1826 the audio material end time VOB₋₋ AEND is extracted foreach VOB from the scenario data St7, and at a time not exceeding theVOB₋₋ AEND time. This time extracted at an audio access unit (AAU) isset as the audio encode end times A₋₋ ENDTM which is an audio encodingparameter. Note that the audio access unit AAU is determined by theaudio encoding method.

At step #1828 the audio start gap A₋₋ STGAP obtained from the differencebetween the video encode start time V₋₋ STTM and the audio encode starttime A₋₋ STTM is defined as a system encode parameter.

At step #1830 the audio end gap A₋₋ ENDGAP obtained from the differencebetween the video encode end time V₋₋ ENDTM and the audio encode endtime A₋₋ ENDTM is defined as a system encode parameter.

At step #1832 the video encoding bit rate V₋₋ BR is extracted from thescenario data St7, and the video encode bit rate V₋₋ RATE, which is theaverage bit rate of video encoding, is set as a video encodingparameter.

At step #1834 the audio encoding bit rate A₋₋ BR is extracted from thescenario data St7, and the audio encode bit rate A₋₋ RATE is set as anaudio encoding parameter.

At step #1836 the video material type VOB₋₋ V₋₋ KIND is extracted fromthe scenario data St7. If the material is a film type, i.e., a movieconverted to television broadcast format (so-called telecineconversion), reverse telecine conversion is set for the video encodemode V₋₋ ENCMD, and defined as a video encoding parameter.

At step #1538 the audio coding method VOB₋₋ A₋₋ KIND is extracted fromthe scenario data St7, and the encoding method is set as the audioencode method A₋₋ ENCMD and set as an audio encoding parameter.

At step #1840 the initial video encode data V₋₋ INTST sets the initialvalue of the VBV buffer to a value less than the VBV buffer end valueset by the last video encode data V₋₋ ENDST, and defined as a videoencoding parameter.

At step #1842 the VOB number VOB₋₋ NO of the preceding connection is setto the preceding VOB number B₋₋ VOB₋₋ NO based on the setting (=1) ofthe preceding VOB seamless connection flag VOB₋₋ Fsb, and set as asystem encode parameter.

At step #1844 the VOB number VOB₋₋ NO of the following connection is setto the following VOB number F₋₋ VOB₋₋ NO based on the setting (=1) ofthe following VOB seamless connection flag VOB₋₋ Fsf, and set as asystem encode parameter.

The encoding information table and encode parameters are thus Generatedfor a multi-angle VOB Set with non-seamless multi-angle switchingcontrol enabled.

The process for generating the encode parameters of a seamless switchingstream with multi-angle control is described below with reference toFIG. 37. This stream is generated when step 1500 in FIG. 34 returns YESand the following flags are set as shown: VOB₋₋ Fsb=1 or VOB₋₋ Fsf=1,VOB₋₋ Fp=1, VOB₋₋ FI=1, VOB₋₋ Fm=1, and VOB₋₋ FsV=1. The followingoperation produces the encoding information tables shown in FIG. 27 andFIG. 28, and the encode parameters shown in FIG. 29.

The following operation produces the encoding information tables shownin FIG. 27 and FIG. 28, and the encode parameters shown in FIG. 29.

At step #1850, the scenario reproduction sequence (path) contained inthe scenario data St7 is extracted, the VOB Set number VOBS₋₋ NO is set,and the VOB number VOB₋₋ NO is set for one or more VOB in the VOB Set.

At step #1852 the maximum bit rate ILV₋₋ BR of the interleaved VOB isextracted from the scenario data St7, and the maximum video encode bitrate V₋₋ MRATE from the encode parameters is set based on the interleaveflag VOB₋₋ Fi setting (=1).

At step #1854, the minimum interleaved unit presentation time ILVU₋₋ MTis extracted from the scenario data St7.

At step #1856, the video encode GOP structure GOPST values N=15 and M=3are set, and the GOP structure fixing flag GOP₋₋ Fxflag is set (=1),based on the multi-scene flag VOB₋₋ Fp setting (=1).

At step #1858, the video encode GOP GOPST is set to "closed GOP" basedon the multi-angle seamless switching flag VOB₋₋ FsV setting (=1), andthe video encoding parameters are thus defined.

Step #1860 is the common VOB data setting routine, which is as describedreferring to the flow chart in FIG. 35. Further description thereof isthus omitted here.

The encode parameters of a seamless switching stream with multi-anglecontrol are thus defined for a VOB Set with multi-angle control asdescribed above.

The process for generating the encode parameters for a system stream inwhich parental lock control is implemented is described below withreference to FIG. 38. This stream is generated when step #1200 in FIG.34 returns NO and step #1304 returns YES, i.e., the following flags areset as shown: VOB₋₋ Fsb=1 or VOB₋₋ Fsf=1, VOB₋₋ Fp=1, VOB₋₋ Fi=1, VOB₋₋Fm=0. The following operation produces the encoding information tablesshown in FIG. 27 and FIG. 28, and the encode parameters shown in FIG.29.

At step #1370, the scenario reproduction sequence (path) contained inthe scenario data St7 is extracted, the VOB Set number VOBS₋₋ NO is set,and the VOB number VOB₋₋ NO is set for one or more VOB in the VOB Set.

At step #1872 the maximum bit rate ILV₋₋ BR of the interleaved VOB isextracted from the scenario data St7, and the maximum video encode bitrate V₋₋ MRATE from the encode parameters is set based on the interleaveflag VOB₋₋ Fi setting (=1).

AT step #1874 the number of interleaved VOB divisions ILV₋₋ DIV isextracted from the scenario data st7.

Step #1876 is the common VOB data setting routine, which is as describedreferring to the flow chart in FIG. 35. Further description thereof isthus omitted here.

The encode parameters of a system stream in which parental lock controlis implemented are thus defined for a VOB Set with multi-scene selectioncontrol enabled as described above.

The process for generating the encode parameters for a system streamcontaining a single scene is described below with reference to FIG. 70.This stream is generated when step #900 in FIG. 34 returns NO, i.e.,when VOB Fp=0. The following operational produces the encodinginformation tables shown in FIG. 27 and FIG. 28, and the encodeparameters shown in FIG. 29.

At step #1880, the scenario reproduction sequence (path) contained inthe scenario data St7 is extracted, the VOB Set number VOBS₋₋ NO is set,and the VOB number VOB₋₋ NO is set for one or more VOB in the VOB set.

At set #1882 the maximum bit rate ILV₋₋ BR of the interleaved VOB isextracted from the scenario data St7, and the maximum video encode bitrate V₋₋ MRATE from the encode parameters is set based on the interleaveflag VOB₋₋ Fi setting (=1).

Step #1884 is the common VOB data setting routine, which is as describedreferring to the flow chart in FIG. 35. Further description thereof isthus omitted here.

These flow charts for defining the encoding information table and encodeparameters thus generate the parameters for DVD video, audio, and systemstream encoding by the DVD formatter.

Flow Chart: Formatter

The operation of the subroutine executed by the DVD formatter shown asstep #2300 in FIG. 34B is described next with reference to FIGS. 49, 59,51, 52, and 53. This formatter subroutine generates the DVD multimediabitstream.

The operation of the DVD encoder ECD 1100 according to the presentinvention is described with reference to the flow chart in FIG. 49. Notethat those steps shown in FIG. 49 with a double line are subroutines.

At step #2310 the program chain information VTS₋₋ PGCI is set to sheVTSI management table VTSI₋₋ MAT for the number of title, TITLE₋₋ NUMbased on the number of titles TITLE₋₋ NUM in the VOB Set data stream.

At step #2312 it is determined whether multi-scene selection control isenabled based on the multi-scene flag VOB₋₋ Fp in the VOB Set datastream. If step #2312 returns NO, i.e., multi-scene control is notenabled, the procedure moves to step #2314.

At step #2314 the operation for coding a single scene (VOB) executed bythe formatter 1100 of the authoring encoder EC shown in FIG. 25 isaccomplished. This routine is described later.

If step #2312 returns YES, i.e., multi-scene control is enabled, theprocedure moves to step #2136.

At step #2316 it is determined whether the information is to beinterleaved or not based on the interleave flag VOB₋₋ Fi state in theVOB Set data stream. If step #2316 returns NO, i.e., the information isnot to be interleaved, the procedure moves to step #2314. If step #2316returns YES, i.e., the information is to be interleaved, the proceduremoves to step #2318.

At step #2318 it is determined whether multi-angle control is to beimplemented based on the multi-angle flag VOB₋₋ Fm in the VOB Set datastream. If step #2318 returns NO, the parental lock control routine instep #2320 is executed. If step #2318 returns YES, the procedure movesto step #2322.

At step #2320 the operation for formatting the VOB Set for parental lockcontrol is executed. This subroutine is shown in FIG. 52 and describedbelow.

At step #2322 it is determined whether multi-angle seamless switching isrequired based on the multi-angle seamless switching flag VOB₋₋ FsV. Ifmulti-angle switching is accomplished without seamless switching, i.e.,with non-seamless switching and step #2322 returns NO, the proceduremoves to step #2326.

The multi-angle non-seamless switching control routine executed in step#2326 by the formatter 1100 of the authoring encoder EC in FIG. 25 isdescribed later with reference to FIG. 50.

If multi-angle switching is accomplished with seamless switchingcontrol, i.e., step #2322 returns YES, the procedure moves to step#2324.

The multi-angle seamless switching control routine executed in step#2324 by the formatter 1100 of the authoring encoder EC in FIG. 25 isdescribed later with reference to FIG. 51.

The cell playback information (PCG information entries C₋₋ PBI) of theVTS information VTSI set as previously described is then recorded.

At step #2330 it is determined whether all VOB Sets declared by the VOBSet number VOBS₋₋ NUM have been processed by the formatter. If NO,control loops back to step #2312, and the process runs again. If YES,all sets have been formatted, the procedure terminates.

Referring to FIG. 50, the multi-angle nonseamless switching controlroutine executed in step #2326 when step #2322, FIG. 49, returns NO isdescribed. This routine defines the interleaved arrangement of themultimedia bitstream. MBS, the content of the cell playback information(C₋₋ PBI#i) shown in FIG. 16, and the information stored to thenavigation pack NV shown in FIG. 20, in the generated DVD multimediabitstream MBS.

At step #2340 based on the multi-angle flag VOB₋₋ Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block mode CBM (FIG. 16) of the cell playbackinformation blocks C₋₋ PBI #i containing the VOB control information foreach scene is declared according to the position of the angle data. Forexample, the cell block mode CBM of the MA1 cell (FIG. 23) is declaredas 01b to indicate the beginning of the cell block, the CBM of MA2 isdeclared as 10b to indicate a cell between the first and last cells inthe block, and the CBM of MA3 is declared as; 11b to indicate the end ofthe cell block.

At step #2342 based on the multi-angle flag VOB₋₋ Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block type CBT (FIG. 16) of the cell playbackinformation blocks C₋₋ PBI #i containing the VOB control information foreach scene is declared as 01b to indicate an "angle."

At step #2344 the seamless playback flag SPF (FIG. 16) is set to 1 inthe cell playback information blocks C₋₋ PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which is set to 1 to indicate aseamless connection.

At step #2346 the STC resetting flag STCDF is set to 1 in the cellplayback information blocks C₋₋ PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which is set to 1 to indicate aseamless connection.

At step #2348 the interleaved allocation flag IAF (FIG. 16) is set to 1in the cell playback information blocks C₋₋ PBI #i containing the VOBcontrol information for each scene based on the multi-angle seamlessswitching flag VOB₋₋ FsV state, which is set to 1 to indicateinterleaving is required.

At step #2350 the location of the navigation pack NV (relative sectorrumber from the VOB beginning) is detected from the title editing unit(VOB below) obtained from the system encoder 900 in FIG. 25, thenavigation pack NV is detected based on the minimum interleaved unitpresentation time ILVU₋₋ MT information (a formatter parameter obtainedin step #1816, FIG. 35), the location of the VOBU expressed as thenumber of sectors from the VOB beginning, for example, is thus obtained,and the title editing unit VOB is divided into interleave units usingVOBU units.

For example, if in this example the minimum interleaved unitpresentation time ILVU₋₋ MT is 2 sec and the presentation time of oneVOBU is 0.5 sec., then the VOB is divided into interleave units of 4VOBU each. Note that this allocation operation is applied to the VOBconstituting each multi-scene data unit.

At step #2352 the interleave units of each VOB obtained from step #2350are arranged in the cell block mode CBM sequence (cell block beginning,middle, and end cells) written as the VOB control information for eachscene in step #2340 to form the interleaved blocks as shown in FIG. 71or 72. The interleaved blocks are then added to the VTS title VOBS(VTSTT₋₋ VOBS). Using the cell block mode CBM declarations above, forexample, the angle data MA1, MA2, and MA3 (FIG. 23) are arranged in thatsequence.

At step #2354 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU₋₋ EA (FIG. 20) in the navigation packNV of each VOBU based on the VOBU position information obtained in step#2350.

At step #2356 the first cell VOBU start address C₋₋ FVOBU₋₋ SA and thelast cell VOBU start address C₋₋ LVOBU₋₋ SA expressed as the number ofsectors from the beginning of the VTS title VOBS (VTSTT₋₋ VOBS) arewritten as the addresses of the navigation packs NV of the first andlast VOBU in each cell based on the VTS title VOBS (VTSTT₋₋ VOBS) dataobtained in step) #2352.

The angle #i VOBU start address NSML₋₋ AGL₋₋ C1₋₋ DSTA-NSML₋₋ AGL₋₋ C9₋₋DSTA of the non-seamless angle information NSML₋₋ AGLI (FIG. 20) in thenavigation pack NV of each VOBU is written at step #2358. This addressis expressed as the relative sector number inside the data of theinterleaved blocks formed in step #2352, and declares the addressinformation (FIG. 50) of the navigation pack NV contained in the VOBU ofall angle scenes near the presentation start time of the VOBU beingprocessed.

At step #2360 "7FFFFFFFh" is written to the angle #i VOBU start addressNSML₋₋ AGL₋₋ C1₋₋ DSTA-NSML₋₋ AGL₋₋ C9₋₋ DSTA of the non-seamless angleinformation NSML₋₋ AGLI (FIG. 20) in the navigation paLck NV of eachVOBU if the VOBU being processed is the last VOBU of each scene in themulti-scene period.

This routine thus formats the interleaved blocks for multi-anglenon-seamless switching control in the multi-scene period, and formatsthe cell control information as the reproduction control information forthose multiple scenes.

Referring to FIG. 51, the multi-angle seamless switching control routineexecuted in step #2324 when step #2322, FIG. 49, returns YES isdescribed. This routine defines the interleaved arrangement of themultimedia bitstream MBS, the content of the cell playback information(C₋₋ PBI#i) shown in FIG. 16, and the information stored to thenavigation pack NV shown in FIG. 20, in the generated DVD multimediabitstream MBS.

At step #2370 based on the multi-angle flag VOB₋₋ Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block mode CBM (FIG. 16) of the cell playbackinformation blocks C₋₋ PBI #i containing the VOB control information foreach scene is declared according to the position of the angle data. Forexample, the cell block mode CBM of the MA1 cell (FIG. 23) is declaredas 01b to indicate the beginning of the cell block, the CBM of MA2 isdeclared as 10b to indicate a cell between the first and last cells inthe block, and the CBM of MA3 is declared as 11b to indicate the end ofthe cell block.

At step #2372 based on the multi-angle flag VOB₋₋ Fm setting (=1)declaring whether multi-angle control is applied in the multi-sceneperiod, the cell block type CBT (FIG. 16) of the cell playbackinformation blocks C₋₋ PBI #i containing the VOB control information foreach scene is declared as 01b to indicate an "angle."

At step #2374 the seamless playback flag SPF (FIG. 16) is set to 1 inthe cell playback information blocks C₋₋ PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which is set to 1 to indicate aseamless connection.

At step #2376 the STC resetting flag STCDF is set to 1 in the cellplayback information blocks C₋₋ PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which is set to 1 to indicate aseamless connection.

At step #2378 the interleaved allocation flag IAF (FIG. 16) is set to 1in the cell playback information blocks C₋₋ PBI #i containing the VOBcontrol information for each scene based on the multi-angle seamlessswitching flag VOB₋₋ FsV state, which is set to 1 to indicateinterleaving is required.

At step #2380 the location of the navigation pack NV (relative sectornumber from the VOB beginning) is detected from the title editing unit(VOB below) obtained from the system encoder 900 in FIG. 25, thenavigation pack NV is detected based on the minimum interleaved unitpresentation time ILVU₋₋ MT information (a formatter parameter obtainedin step #1854, FIG. 37), the location of the VOBU expressed as thenumber of sectors from the VOB beginning, for example, is thus obtained,and the title editing unit VOB is divided into interleave units usingVOBU units.

For example, if in this example the minimum interleaved unitpresentation time ILVU₋₋ MT is 2 sec and the presentation time of coneVOBU is 0.5 sec., then the VOB is divided into interleave units of 4VOBU each. Note that this allocation operation is applied to the VOBconstituting each multi-scene data unit.

At step #2332 the interleave units of each VOB obtained from step #2380are arranged in the cell block mode CBM sequence (cell block beginning,middle, and end cells) written as the VOB control information for eachscene in step #2360 to form the interleaved blocks as shown in FIG. 71or 72. The interleaved blocks are then added to the VTS title VOBS(VTSTT₋₋ VOBS). Using the cell block mode CBM declarations above, forexample, the angle data MA1, MA2, and MA3 (FIG. 23) are arranged in thatsequence.

At step #2384 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU EA (FIG. 20) in the navigation pack NVof each VOBU based on the VOBU position information obtained in step#2360.

At step #2386 the first cell VOBU start address C₋₋ FVOBU₋₋ SA and theleast cell VOBU start address C₋₋ LVOBU₋₋ SA expressed as the number ofsectors from the beginning of the VTS title VOBS (VTSTT₋₋ VOBS) arewritten as the addresses of the navigation packs NV of the first andlast VOBU in each cell based on the VTS title VOBS (VTSTT₋₋ VOBS) dataobtained in step #2382.

At step #2388 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU₋₋ EA (FIG. 20) in the navigation packNV of each VOBU based on the interleave unit data obtained in step#2370.

The angle #i VOBU start address SML₋₋ AGL₋₋ C1₋₋ DSTA-SML₋₋ AGL₋₋ C9₋₋DSTA of the seamless angle information SML₋₋ AGLI (FIG. 20) in thenavigation pack NV of each VOBU is written at step #2390. This addressis expressed as the relative sector number inside the data of theinterleaved blocks formed in step #2382, and declares the addressinformation of the navigation pack NV contained in the VOBU of all anglescenes with a start time contiguous to the reproduction end time of theVOBU being processed.

At step #2392 "7FFFFFFFh" is written to the angle #i VOBU start addressSML₋₋ AGL₋₋ C1₋₋ DSTA-SML₋₋ AGL₋₋ C9₋₋ DSTA of the seamless angleinformation SML₋₋ AGLI (FIG. 20) in the navigation pack NV of the VOBUcontained in the interleaved unit if the interleave unit arranged instep #2382 is the last interleave unit of each scene in the multi-sceneperiod.

This routine thus formats the interleaved blocks for multi-angleseamless switching control in the multi-scene period, and formats thecell control information as the reproduction control information forthose multiple scenes.

The parental lock subroutine (step #2320, FIG. 49) executed when step#2318 in FIG. 49 returns NO, i.e., when it is determined that parentallock control is implemented and not multi-angle control, is describednext with reference to FIG. 52.

The parental lock subroutine described below writes the interleave unitarrangement of the multimedia bitstream, the content of the PGCinformation entries C₋₋ PBI #i (cell playback information) shown in FIG.16, and the navigation pack NV information shown in FIG. 20, to thegenerated DVD multimedia bitstream.

At step #2402 a value "00" is written to the cell block mode CBM (FIG.16) of the cell playback information blocks C₋₋ PBI #i containing theVOB control information for each scene based on the multi-angle flagVOB₋₋ Fm state, which is set to 0 to indicate that multi-angle controlis not enabled in the multi-scene period.

At step #2404 the seamless playback flag SPF (FIG. 16) is set to 1 inthe cell playback information blocks C₋₋ PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which is set to 1 to indicate aseamless connection.

At step #2406 the STC resetting flag STCDF is set to 1 in the cellplayback information blocks C₋₋ PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which is set to 1 to indicate aseamless connection.

At step #2408 the interleaved allocation flag IAF (FIG. 16) is set to 1in the cell playback information blocks C₋₋ PBI #i containing the VOBcontrol information for each scene based on the multi-angle seamlessswitching flag VOB₋₋ FSV state, which is set to 1 to indicateinterleaving is required.

At step #2410 the navigation pack NV position information (the relativesector number from the VOB start) is detected from the title editingunit (VOB) obtained from the system encoder 900 (FIG. 25). Thenavigation pack NV is then detected based on the number of interleavedVOB divisions ILV₋₋ DIV, a formatter parameter obtained in step #1874 inFIG. 38, to obtain the VOBU position information (number of sectors fromthe VOB start), and divide each VOB into the specified number ofinterleave units in VOBU units.

At step #2412 the interleave units obtained in step #2410 are theninterleaved. For example, the interleave units are arranged in ascendingVOB number sequence to create the interleaved blocks as shown in FIG. 71or 72, and the interleaved blocks are added to the VTS title VOBS(VTSTT₋₋ VOBS).

At step #2414 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU₋₋ EA (FIG. 20) in the navigation packNV of each VOBU based on the VOBU position information obtained in step#2186.

At step #2416 the first cell VOBU start address C₋₋ FVOBU₋₋ SA and thelast cell VOBU start address C₋₋ LVOBU₋₋ SA expressed as the number ofsectors from the beginning of the VTS title VOBS (TTSTT₋₋ VOBS) arewritten as the addresses of the navigation packs NV of the first andlast VOBU in each cell based on the VTS title VOBS (VTSTT₋₋ VOBS) dataobtained in step #2412.

At step #2418 the relative sector number to the last interleave unitpack is written to the ILVU end pack address ILVU₋₋ EA in the navigationpack NV of the VOBU forming the interleaved units based on theinterleaved unit data obtained from step #2412.

At step #2420, the relative sector number in the interleaved block dataformed in step #2412 is written to the next-ILVU start address NT₋₋ILVU₋₋ SA as the position information of the next ILVU in the navigationpacks NV of the VOBU contained in the interleaved unit ILVU.

At step #2422 the interleaved unit flag ILVU flag is set to 1 in thenavigation packs NV of the VOBU contained in the interleaved unit ILVU.

At step #2424, the Unit END flag of the navigation pack NV in the lastVOBU of the interleaved unit ILVU is set to 1.

At step #2426 "FFFFFFFFh" is written to the next-ILVU start address NT₋₋ILVU₋₋ SA of the navigation pack NV of the VOBU in the last interleavedunit ILVU of each VOB.

The operation described above thus formats the interleaved blocks toenable parental lock control in the multi-scene periods, and formats thecontrol information in the cells, i.e., the cell playback controlinformation for the multi-scene periods.

The single scene subroutine executed as step #2314 in FIG. 49 when steps#2312 or #2316 return NO, i.e. when the scene is (determined to be asingle scene and not a multi-scene period, is described next using FIG.53.

The single scene subroutine described below writes the interleave unitarrangement of the multimedia bitstream, the content of the PGCinformation entries C₋₋ PBI #i (cell playback information) shown in FIG.16, and the navigation pack NV information shown in FIG. 20, to thegenerated DVD multimedia bitstream.

At step #2430 a value "00" indicating a "non-cell block", i.e., thatthere is only one cell in the functional block, is written to the cellblock mode CBM (FIG. 16) of the cell playback information blocks C₋₋ PBI#i containing the VOB control information for each scene based on themulti-scene flag VOB₋₋ Fp state, which is set to 0 to indicate that thescene is a single scene and not part of a multi-scene period.

At step #2132 the interleaved allocation flag IAF (FIG. 16) is set to 0in the cell playback information blocks C₋₋ PBI #i containing the VOBcontrol information for each scene based on she multi-angle seamlessswitching flag VOB₋₋ FsV state, which is set to 0 to indicateinterleaving is not required.

At step #2434 the navigation pack NV position information (the relativesector number from the VOB start) is detected from the title editingunit (VOB) obtained from the system encoder 900 (FIG. 25), placed in theVOBU unit, and added to the VTS title VOBS (VTSTT₋₋ VOBS), the video andother stream data of the multimedia bitstream.

At step #2436 the relative sector number from the VOBU start is writtento the VOB end pack address VOBU₋₋ EA (FIG. 20) in the navigation packNV of each VOBU based on the VOBU position information obtained in step#2434.

At step #2438 the first cell VOBU start address C₋₋ FVOBU₋₋ SA and thelast cell VOBU start address C₋₋ LVOBU₋₋ SA expressed as the number ofsectors from the beginning of and the end of, respectively, the VTStitle VOBS (VTSTT₋₋ VOBS) of the value written as the addresses of thenavigation packs NV of the first and last VOBU in cell based on the VTStitle VOBS (VTSTT₋₋ VOBS) data obtained in step #2434.

At step #2440 the state determined as a result of step #300 or #600 inFIG. 34, i.e., whether preceding VOB seamless connection flag VOB₋₋ Fsbis set to 1 indicating a seamless connection to the preceding orfollowing scenes, is evaluated. If step #2440 returns YES, the proceduremoves to step #2442.

At step #2142 the seamless playback flag SPF (FIG. 16) is set to 1 inthe cell playback information blocks C₋₋ PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which is set to 1 to indicate aseamless connection.

At step #2444 the STC resetting flag STCDF is set to 1 in the cellplayback information blocks C₋₋ PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which is set to 1.

If step #2440 returns NO, i.e., there is not a seamless connection tothe preceding scene, the procedure moves to step #2446.

At step #2446 the seamless playback flag SPF (FIG. 16) is set to 0 inthe cell playback information blocks C₋₋ PBI #i containing the VOBcontrol information for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which-is set to 0 to indicate anon-seamless connection.

At step #2448 the STC resetting flag STCDF is set to 0 in the cellplayback information blocks C₋₋ PBI #i containing the VOB controlinformation for each scene based on the preceding VOB seamlessconnection flag VOB₋₋ Fsb state, which is set to 0.

The operation described above thus formats a multimedia bitstream for asingle scene period, and records the control information in the cells,i.e., the cell playback control information (C₋₋ PBI #i, FIG. 16), andthe information in the navigation pack NV (FIG. 20), to the produced DVDmultimedia bitstream.

Decoder Flow Charts

A. Disk-to-stream buffer transfer flow:

The decoding information table produced by the decoding systemcontroller 2300 based on the scenario selection data St51 is describedbelow referring to FIGS. 54 and 55. The decoding information tablecomprises the decoding system table shown in FIG. 54, and the decodingtable shown in FIG. 55.

As shown in FIG. 54, the decoding system table comprises a scenarioinformation register and a cell information register. The scenarioinformation register records the title number and other scenarioreproduction information selected by the user and extracted from thescenario selection data St51. The cell information register extracts andrecords the information required to reproduce the cells constituting theprogram chain PGC based on the user-defined scenario informationextracted into the scenario information register.

More specifically, the scenario information register contains pluralsub-registers, i.e., the angle number ANGLE₋₋ NO₋₋ reg, VTS number VTS₋₋NO₋₋ reg, PGC number VTS₋₋ PGCI₋₋ NO₋₋ reg, audio ID₋₋ AUDIO₋₋ ID₋₋ reg,sub-picture ID SP₋₋ ID₋₋ reg, and the system clock reference SCR bufferSCR₋₋ buffer.

The angle number ANGLE₋₋ NO₋₋ reg stores which angle is reproduced whenthere are multiple angles in the reproduction program chain PGC.

The VTS number VTS₋₋ NO₋₋ reg records the number of the next VTSreproduced from among the plural VTS on the disk.

The PGC number VTS₋₋ PGCI₋₋ NO₋₋ reg records which of the plural programchains PGC present in the video title set VTS is to be reproduced forparental lock control or other applications.

The audio ID AUDIO₋₋ ID₋₋ reg records which of the plural audio streamsin the VTS are to be reproduced.

The sub-picture ID₋₋ SP₋₋ ID₋₋ reg records which of the pluralsub-picture streams is to be reproduced when there are pluralsub-picture streams in the VTS.

The system clock reference SCR buffer SCR₋₋ buffer is the buffer fortemporarily storing the system clock reference SCR recorded to the packheader as shown in FIG. 19. As described using FIG. 26, this temporarilystored system clock reference SCR is output to the decoding systemcontroller 2300 as the bitstream control data St63.

The cell information register contains the following sub-registers: thecell block mode CBM₋₋ reg, cell block type CBT₋₋ reg, seamlessreproduction flag SPF₋₋ reg, interleaved allocation flag IAF₋₋ reg, STCresetting flag STCDF₋₋ reg, seamless angle change flag SACF₋₋ reg, firstcell VOBU start address C₋₋ FVOBU₋₋ SA₋₋ reg, and last cell VOBU startaddress C₋₋ LVOBU₋₋ SA₋₋ reg.

The cell block mode CBM₋₋ reg stores a value indicating whether pluralcells constitute one functional block. If there are not plural cells inone functional block, CBM₋₋ reg stores N₋₋ BLOCK. If plural cellsconstitute one functional block, the value F₋₋ CELL is stored as theCBM₋₋ reg value of the first cell in the block, L₋₋ CELL is stored asthe CBM₋₋ reg value of the last cell in the block, and BLOCK is storedas the CBM₋₋ reg of value all cells between the first and Last cells inthe block.

The cell block type CBT₋₋ reg stores a value defining the type of theblock indicated by the cell block mode CBM₋₋ reg. If the cell block is amulti-angle block, A₋₋ BLOCK is stored; if not, N₋₋ BLOCK is stored.

The seamless reproduction flag SPF₋₋ reg stores a value defining whetherthat cell is seamless connected with the cell or cell block reproducedtherebefore. If a seamless connection is specified, SML is stored; if aseamless connection is not specified, NSML is stored.

The interleaved allocation flag IAF₋₋ reg stores a value identifyingwhether the cell exists in a contiguous or interleaved block. If thecell is part of a an interleaved block, ILVB is stored; otherwise N₋₋ILVB is stored.

The STC resetting flag STCDF₋₋ reg defines whether the system time clockSTC used for synchronization must be reset when the cell is reproduced;when resetting the system time clock STC is necessary, STC₋₋ RESET isstored; if resetting is not necessary, STC₋₋ NRESET is stored.

The seamless angle change flag SACF reg stores a value indicatingwhether a cell in a multi-angle period should be connected seamlessly atan angle change. If the angle change is seamless, the seamless anglechange flag SACF is set to SML; otherwise it is set to NSML.

The first cell VOBU start address C₋₋ FVOBU₋₋ SA₋₋ reg stores the VOBUstart address of the first cell in a block. The value of this address isexpressed as the distance from the logic sector of the first cell in theVTS title VOBS (VTSTT₋₋ VOBS) as measured by and expressed (stored) asthe number of sectors.

The last cell VOBU start address C₋₋ LVOBU₋₋ SA₋₋ reg stores the VOBUstart address of the last cell in the block. The value of this addressis also expressed as the distance from the logic sector of the firstcell in the VTS title VOBS (VTSTT₋₋ VOBS) measured by and expressed(stored) as the number of sectors.

The decoding table shown in FIG. 55 is described below. As shown in FIG.55, the decoding table comprises the following registers: informationregisters for non-seamless multi-angle control, information registersfor seamless multi-angle control, a VOBU information register, andinformation registers for seamless reproduction.

The information registers for non-seamless multi-angle control comprisesub-registers NSML₋₋ AGL₋₋ C1₋₋ DSTA₋₋ reg-NSML₋₋ AGL₋₋ C9₋₋ DSTA₋₋ reg.

NSML₋₋ AGL₋₋ C1₋₋ DSTA₋₋ reg-NSML₋₋ AGL₋₋ C9₋₋ DSTA₋₋ reg record theNMSL₋₋ AGL₋₋ C1₋₋ DSTA-NMSL₋₋ AGL₋₋ C9₋₋ DSTA values in the PCI packetshown in FIG. 20.

The information registers for seamless multi-angle control comprisesub-registers SML₋₋ AGL₋₋ C1₋₋ DSTA₋₋ reg-SML₋₋ AGL₋₋ C9₋₋ DSTA₋₋ reg.

SML₋₋ AGL₋₋ C1₋₋ DSTA₋₋ reg-SML₋₋ AGL₋₋ C9₋₋ DSTA₋₋ reg record the SML₋₋AGL₋₋ C1₋₋ DSTA-SML₋₋ AGL₋₋ C9₋₋ DSTA values in the DSI packet shown inFIG. 20.

The VOBU information register stores the end pack address VOBU₋₋ EA inthe DSI packet shown in FIG. 20.

The information registers for seamless reproduction comprise thefollowing sub-registers: an interleaved unit flag ILVU₋₋ flag₋₋ reg,Unit END flag UNIT₋₋ END₋₋ flag₋₋ reg, Interleaved Unit End AddressILVU₋₋ EA₋₋ reg, Next Interleaved Unit Start Address NT₋₋ ILVU₋₋ SA₋₋reg, the presentation start time of the first video frame in the VOB(Initial Video Frame Presentation Start Time) VOB₋₋ V₋₋ SPTM₋₋ reg, thepresentation end time of the last video frame in the VOB (Final VideoFrame Presentation Termination Time) VOB₋₋ V₋₋ EPTM₋₋ reg, audioreproduction stopping time 1 VOB₋₋ A₋₋ STP₋₋ PTM1₋₋ reg, audioreproduction stopping time 2 VOB₋₋ A₋₋ STP₋₋ PTM2₋₋ reg, audioreproduction stopping period 1 VOB₋₋ A₋₋ GAP₋₋ LEN1₋₋ reg, and audioreproduction stopping period 2 VOB₋₋ A₋₋ GAP₋₋ LEN2₋₋ reg.

The interleaved unit flag ILVU₋₋ flag₋₋ reg stores the value indicatingwhether the video object unit VOBU is in an interleaved block, andstores ILVU if it is, and N₋₋ ILVU if not.

The Unit END flag UNIT₋₋ END₋₋ flag₋₋ reg stores the value indicatingwhether the video object unit VOBU is the last VOBU in the interleavedunit ILVU. Because the interleaved unit ILVU is the data unit forcontinuous reading, the UNIT₋₋ END₋₋ flag₋₋ reg stores END if the VOBUcurrently being read is the last VOBU in the interleaved unit ILVU, andotherwise stores N₋₋ END.

The Interleaved Unit End Address ILVU₋₋ EA₋₋ reg stores the address ofthe last pack in the ILVU to which the VOBU belongs if the VOBU is in aninterleaved block. This address is expressed as the number of sectorsfrom the navigation pack NV of that VOBU.

The Next Interleaved Unit Start Address NT₋₋ ILVU₋₋ SA₋₋ reg stores thestart address of the next interleaved unit ILVU if the VOBU is in aninterleaved block. This address is also expressed as the number ofsectors from the navigation pack NV of that VOBU.

The Initial Video Frame Presentation Start Time register VOB₋₋ V₋₋SPTM₋₋ reg stores the time at which presentation of the first videoframe in the VOB starts.

The Final Video Frame Presentation Termination Time register VOB₋₋ V₋₋EPTM₋₋ reg stores the time at which presentation of the last video framein the VOB ends.

The audio reproduction stopping time 1 VOB₋₋ A₋₋ STP₋₋ PTM1₋₋ reg storesthe time at which the audio is to be paused to enable resynchronization,and the audio reproduction stopping period 1 VOB₋₋ A₋₋ GAP₋₋ LEN1₋₋ regstores the length of this pause period.

The audio reproduction stopping time 2 VOB₋₋ A₋₋ STP₋₋ PTM2₋₋ reg andaudio reproduction stopping period 2 VOB₋₋ A₋₋ GAP₋₋ LEN2₋₋ reg storethe same values.

The operation of the DVD decoder DCD according to the present inventionas shown in FIG. 26 is described next below with reference to the flowchart in FIG. 56.

At step #310202 it is first determined whether a disk has been inserted.If it has, the procedure moves to step #310204.

At step #310204, the volume file structure VFS (FIG. 21) is read, andthe procedure moves to step #310206.

At step #310206, the video manager VMG (FIG. 21) is read and the videotitle set VTS to be reproduced is extracted. The procedure then moves tostep #310208.

At step #310208, the video title set menu address information VTSM₋₋ C₋₋ADT is extracted from the VTS information VTSI, ard the procedure movesto step #310210.

At step #310210 the video title set menu VTSM₋₋ VOBS is read from thedisk based on the video title set menu address information VTSM₋₋ C₋₋ADT, and the title selection menu is presented.

The user is thus able to select the desired title from this menu in step#310212. If the titles include both contiguous titles with nouser-selectable content, and titles containing audio numbers,sub-picture numbers, or multi-angle scene content, the user must alsoenter the desired angle number. Once the user selection is completed,the procedure moves to step #310214.

At step #310214, the VTS₋₋ PGCI #i program chain (PGC) data blockcorresponding to the title number selected by the user is extracted fromthe VTSPGC information table VTS₋₋ PGCIT, and the procedure moves tostep #310216.

Reproduction of the program chain PGC then begins at step #310216. Whenprogram chain PGC reproduction is finished, the decoding process ends.If a separate title is thereafter to be reproduced as determined bymonitoring key entry to the scenario selector, the title menu ispresented again (step #310210).

Program chain reproduction in step #310216 above is described in furtherdetail below referring to FIG. 57. The program chain PGC reproductionroutine consists of steps #31030, #31032, #31034, and #31035 as shown.

At step #31030 the decoding system table shown in FIG. 54 is defined.The angle number ANGLE₋₋ NO₋₋ reg, VTS number VTS₋₋ NO₋₋ reg, PGC numberVTS₋₋ PGCI₋₋ NO₋₋ reg, audio ID AUDIO₋₋ ID₋₋ reg, and sub-picture IDSP₋₋ ID₋₋ reg are set according to the selections made by the user usingthe scenario selector 2100.

Once the PGC to be reproduced is determined, the corresponding cellinformation (PGC information entries C₋₋ PBI #j) is extracted and thecell information register is defined. The sub-registers therein that aredefined are the cell block mode CBM₋₋ reg, cell block type CBT₋₋ reg,seamless reproduction flag SPF₋₋ reg, interleaved allocation flag IAF₋₋reg, STC resetting flag STCDF, seamless angle change flag SACF₋₋ reg,first cell VOBU start address C₋₋ FVOBU₋₋ SA₋₋ reg, and last cell VOBUstart address C₋₋ LVOBU₋₋ SA₋₋ reg.

Once the decoding system table is defined, the process transferring datato the stream buffer (step #31032) and the process decoding the data inthe stream buffer (step #31034) are activated in parallel.

The process transferring data to the stream buffer (step #31032) is theprocess of transferring data from the recording medium M to the streambuffer 2400. This is, therefore, the processing of reading the requireddata from the recording medium M and inputting the data to the streambuffer 2400 according to the user-selected title information and theplayback control information (navigation packs NV) written in thestream.

The routine shown as step #31034 is the process for decoding the datastored to the stream buffer 2400 (FIG. 26), and outputting the decodeddata to the video data output terminal 3600 and audio data outputterminal 3700. Thus, is the process for decoding and reproducing thedata stored to the stream buffer 2400.

Note that step #31032 and step #31034 are executed in parallel.

The processing unit of step #31032 is the cell, and as processing onecell is completed, it is determined in step #31035 whether the completeprogram chain PGC has been processed. If processing the complete programchain PGC is not completed, the decoding system table is defined for thenext cell in step #31030. This loop from step #31030 through step 031035is repeated until the entire program chain PGC is processed.

The stream buffer data transfer process of step #31032 is described infurther detail below referring to FIG. 62. The stream buffer datatransfer process (step #31032) comprises steps #31040, #31042, #31044,#31046, and #31048 shown in the figure.

At step #31040 it is determined whether the cell is a multi-angle cell.If not, the procedure moves to step #30144.

At step #31044 the non-multi-angle cell decoding process is executed.

However, if step #30140 returns YES because the cell is a multi-anglecell, the procedure moves to step #30142 where the seamless angle changeflag SACF is evaluated to determine whether seamless angle reproductionis specified.

If seamless angle reproduction is specified, the seamless multi-angledecoding process is executed in step #30146. If seamless anglereproduction is not specified, the non-seamless multi-angle decodingprocess is executed in step #30148.

The non-multi-angle cell decoding process (step #31044, FIG. 62) isdescribed further below with reference to FIG. 63. Note that thenon-multi-angle cell decoding process (step #31044) comprises the steps#31050, #31052, and #31054.

The first step #31050 evaluates the interleaved allocation flag IAF₋₋reg to determine whether the cell is in an interleaved block. If it is,the non-multi-angle interleaved block process is executed in step#31052.

The non-multi-angle interleaved block process (step #31052) processesscene branching and connection where seamless connections are specifiedin, for example, a multi-scene period.

However, if the cell is not in an interleaved block, the non-multi-anglecontiguous block process is executed in step #31054. Note that the step#31054 process is the process executed when there is no scene branchingor connection.

The non-multi-angle interleaved block process (step #31052, FIG. 63) isdescribed further below with reference to FIG. 64.

At step #31060 the reading head 2006 is jumped to the first cell VOBUstart address C₋₋ FVOBU₋₋ SA read from the C₋₋ FVOBU₋₋ SA reg register.

More specifically, the address data C₋₋ FVOBU₋₋ SA₋₋ reg store(d in thedecoding system controller 2300 (FIG. 26) is input as bitstreamreproduction control signal St53 to the reproduction controller 2002.The reproduction controller 2002 thus controls the recording media driveunit 2004 and signal processor 2008 to move the reading head 2006 to thespecified address, data is read, error correction code ECC and othersignal processing is accomplished by the signal processor 2008, and thecell start VOBU data is output as the reproduced bitstream St61 to thestream buffer 2400. The procedure then moves to step #31062.

At step #31062 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31064. The registers set in thedecoding table are the ILVU₋₋ EA₋₋ reg, NT₋₋ ILVU₋₋ SA₋₋ reg, VOB₋₋ V₋₋SPTM₋₋ reg, VOB₋₋ V₋₋ EPTM₋₋ reg, VOB₋₋ A₋₋ STP₋₋ PTM1₋₋ reg, VOB₋₋ A₋₋STP₋₋ PTM2₋₋ reg, VOB₋₋ A₋₋ GAP₋₋ LEN1₋₋ reg, and VOB₋₋ A₋₋ GAP₋₋ LEN2₋₋reg.

At step #31064 the data from the first cell VOBU start address C₋₋FVOBU₋₋ SA₋₋ reg to the ILVU end pack address ILVU₋₋ EA₋₋ reg, i.e., thedata for one interleaved unit ILVU, is transferred to the stream buffer2400. The procedure then moves to step #31066.

More specifically, the address data ILVU₋₋ EA₋₋ reg stored in thedecoding system controller 2300 (FIG. 26) is supplied to thereproduction controller 2002. The reproduction controller 2002 thuscontrols the recording media drive unit 2004 and signal processor 2008to read the data to the ILVU₋₋ EA₋₋ reg address, and after errorcorrection code ECC and other signal processing is accomplished by thesignal processor 2008, the data for the first ILVU in the cell is outputas the reproduced bitstream St61 to the stream buffer 2400. It is thuspossible to output the data for one contiguous interleaved unit ILVU onthe recording medium M to the stream buffer 2400.

At step #31066 it is determined whether all interleaved units in theinterleaved block have been read and transferred. If the interleavedunit ILVU processed is the last ILVU in the interleaved block,"0x7FFFFFFF" indicating termination is set to the next-ILVU startaddress NT₋₋ ILVU₋₋ SA₋₋ reg as the next read address. If allinterleaved units in the interleaved block have thus been processed, theprocedure moves to step #31068.

At step #31068 the reading head 2006 is again jumped to the address NT₋₋ILVU₋₋ SA₋₋ reg of the next interleave unit to be reproduced, and theprocedure loops back to step #31062. Note that this jump is alsoaccomplished as described above, and the loop from step #31062 to step#31068 is repeated.

However, if step #31066 returns YES, i.e., all interleaved unit ILVU inthe interleaved block have been transferred, step #31052 terminates.

The non-multi-angle interleaved block process (step #31052) thustransfers the data of one cell to the stream buffer 2400.

The non-multi-angle contiguous block process is executed in step #31054,FIG. 63, is described further below with reference to FIG. 65.

At step #33070 the reading head 2006 is jumped to the first cell VOBUstart address C₋₋ FVOBU₋₋ SA read from the C₋₋ FVOBU₋₋ SA₋₋ regregister. This jump is also accomplished as described above, and theloop from step #31072 to step #31076 is initiated.

At step #31072 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31074. The registers set in thedecoding table are the VOBU₋₋ EA₋₋ reg, VOB₋₋ V₋₋ SPTM₋₋ reg, VOB₋₋ V₋₋EPTM₋₋ reg, VOB₋₋ A₋₋ STP₋₋ PTM1₋₋ reg, VOB₋₋ A₋₋ STP₋₋ PTM2₋₋ reg,VOB₋₋ A₋₋ GAP₋₋ LEN1₋₋ reg, and VOB₋₋ A₋₋ GAP₋₋ LEN2₋₋ reg.

At step #31074 the data from the first cell VOBU start address C₋₋FVOBU₋₋ SA₋₋ reg to the end pack address VOBU₋₋ EA reg, i.e., the datafor one video object unit VOBU, is transferred to the stream buffer2400. The procedure then moves to step #31076. The data for one videoobject unit VOBU contiguously arrayed to the recording medium M can thusbe transferred to the stream buffer 2400.

At step #31076 it is determined whether all cell data has beentransferred. If all VOBU in the cell has not been transferred, the datafor the next VOBU is read continuously, and the process loops back tostep #31070.

However, if all VOBU data in the cell has been transferred as determinedby the C₋₋ LVOBU₋₋ SA₋₋ reg value in step #31076, the non-multi-anglecontiguous block process (step #31054) terminates. This process thustransfers the data of one cell to the stream buffer 2400.

Another method of accomplishing the non-multiangle cell decoding process(step #31044, FIG. 62) is described below with reference to FIG. 66.

At step #31080 the reading head 2006 is jumped to the first cell VOBUstart address C₋₋ FVOBU₋₋ SA₋₋ reg, and the first VOBU data in the cellis transferred to the stream buffer 2400. The procedure then moves tostep #31081.

At step #31081 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31082. The registers set in thedecoding table are the SCR₋₋ buffer, VOBU₋₋ EA₋₋ reg, ILVU₋₋ flag₋₋ reg,UNIT₋₋ END₋₋ flag₋₋ reg, ILVU₋₋ EA₋₋ reg, NT₋₋ ILVU₋₋ SA₋₋ reg, VOB₋₋V₋₋ SPTM₋₋ reg, VOB₋₋ V₋₋ EPTM₋₋ reg, VOB₋₋ A₋₋ STP₋₋ PTM1₋₋ reg, VOB₋₋A₋₋ STP₋₋ PTM2 reg, VOB₋₋ A₋₋ GAP₋₋ LEN1₋₋ reg, and VOB₋₋ A₋₋ GAP₋₋LEN2₋₋ reg.

At step #31082 the data from the first cell VOBU start address C₋₋FVO13U₋₋ SA₋₋ reg to the end pack address VOBU₋₋ EA₋₋ reg, i.e., thedata for one video object unit VOBU, is transferred to the stream buffer2400. The procedure then moves to step #31083.

At step #31083 is determined whether all cell VOBU data has beentransferred. If it has, the process (step #31044) terminates. If it hasnot, the procedure moves to step #31084.

At step #31084 it is determined whether the VOBU is the last VOBU in theinterleaved unit. If not, the process loops back to step #31081. If so,the procedure advances to step #31085. It is thus possible to transferone cell of data in VOBU units to the stream buffer 2400.

The loop from step #31081 to step #31084 repeats as described above.

At step #31085 it is determined whether the interleaved unit ILVU is thelast in the interleaved block. If so, step #31044 terminates. If not,the procedure advances to step #31086.

At step #31086 the reading head 2006 is jumped to the address NT₋₋ILVU₋₋ SA₋₋ reg of the next interleave unit, and the procedure loopsback to step #31081. It is thus possible to transfer the data for onecell to the stream buffer 2400.

The seamless multi-angle decoding process executed in step #31046, FIG.62, is described below referring to FIG. 67.

At step #31090 the reading head 2006 is jumped to the first cell VOBUstart address C₋₋ FVOBU₋₋ SA read from the C₋₋ FVOBU₋₋ SA₋₋ regregister, and the first VOBU data in the cell is transferred to thestream buffer 2400. The procedure then moves to step #31091. This jumpis also accomplished as described above, and the loop from step #31091to step #31095 is initiated.

At step #31091 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31092. The registers set in thedecoding table are the ILVU₋₋ EA₋₋ reg, SML₋₋ AGL₋₋ C1₋₋ DSTA₋₋ regSML₋₋ AGL₋₋ C9₋₋ DSTA₋₋ reg, VOB₋₋ V₋₋ SPTM₋₋ reg, VOB₋₋ V₋₋ EPTM₋₋ reg,VOB₋₋ A₋₋ STP₋₋ PTM1₋₋ reg, VOB₋₋ A₋₋ STP₋₋ PTM2₋₋ reg, VOB₋₋ A₋₋ GAP₋₋LENI₋₋ reg, and VOB₋₋ A₋₋ GAP₋₋ LEN2₋₋ reg.

At step #31092 the data from the first cell VOBU start address C₋₋FVOBIJ₋₋ SA₋₋ reg to the ILVU end pack address ILVU₋₋ EA₋₋ reg, i.e.,the data for one ILVU, is transferred to the stream buffer 2400. Theprocedure then moves to step #31093. It is thus possible to output thedata for one contiguous interleaved unit ILVU on the recording medium Mto the stream buffer 2400.

At step #31093 the ANGLE₋₋ NO₋₋ reg is updated, and the procedure movesto step #31094. This update operation resets the ANGLE₋₋ NO₋₋ reg to theangle number of the angle selected by the user when the user changes theangle using the scenario selector 2100 (FIG. 26).

At step #31094 it is determined whether the angle cell data has all beentransferred. If all ILVU in the cell have not been transferred, theprocedure moves to step #31095. If all ILVU in the cell have beentransferred, the process terminates.

At step #31095 the reading head 2006 is jumped to the next angle (SML₋₋AGL₋₋ C#n₋₋ reg), and the process loops back to step #31091. Note thatSML₋₋ AGL₋₋ C#n₋₋ reg is the address of the angle to which the ANGLE₋₋NO₋₋ reg was updated in step #31093.

It is thus possible to transfer the data for the angle selected by theuser to the stream buffer 2400 in ILVU units.

The non-seamless multi-angle decoding process is executed in step#30148, FIG. 62, is described below referring to FIG. 68.

At step #31100 the reading head 2006 is jumped to the first cell VOBUstart address C₋₋ FVOBU₋₋ SA read from the C₋₋ FVOBU₋₋ SA₋₋ regregister, and the first VOBU data in the cell is transferred to thestream buffer 2400. The procedure then moves to step #31101. This jumpis also accomplished as described above, and the loop from step #31101to step #31105 is initiated.

At step #31101 the DSI packet data in the navigation pack NV (FIG. 20)is extracted in the stream buffer 2400, the decoding table is defined,and the procedure moves to step #31102. The registers set in thedecoding table are the VOBU₋₋ EA₋₋ reg, NSML₋₋ AGL₋₋ C1₋₋ DSTA₋₋ reg,NSML₋₋ AGL₋₋ C9₋₋ DSTA₋₋ reg, VOB₋₋ V₋₋ SPTM₋₋ reg, VOB₋₋ V₋₋ EPTM₋₋reg, VOB₋₋ A₋₋ STP₋₋ PTM1₋₋ reg, VOB₋₋ A₋₋ STP₋₋ PTM2₋₋ reg, VOB₋₋ A₋₋GAP₋₋ LEN1₋₋ reg, and VOB₋₋ A₋₋ GAP₋₋ LEN2₋₋ reg.

At step #1102 the data from the first cell VOBU start address C₋₋FVOBsU₋₋ SA₋₋ reg to the end pack address VOBU₋₋ EA₋₋ reg, i.e., thedata for one VOBU, is transferred to the stream buffer 2400. Theprocedure then moves to step #31103. It is thus possible to output thedata for one contiguous video object unit VOBU on the recording medium Mto the stream buffer 2400.

At step #31103 the ANGLE₋₋ NO₋₋ reg is updated, and the procedure movesto step #31104. This update operation resets the ANGLE₋₋ NO₋₋ reg to theangle number of the angle selected by the user when the user changes theangle using the scenario selector 2100 (FIG. 26).

At step #31104 it is determined whether the angle cell data has all beentransferred. If all VOBU in the cell have not been transferred, theprocedure moves to step #31105. If all VOBU in the cell have beentransferred, the process terminates.

At step #31105 the reading head 2006 is jumped to the next angle (NSML₋₋AGL₋₋ C#n₋₋ reg), and the process advances to step #31106. Note thatNSML₋₋ AGL₋₋ C#n₋₋ reg is the address of the angle to which the ANGLE₋₋NO₋₋ reg was updated in step #31103.

It is thus possible to transfer the data for the angle selected by theuser to the stream buffer 2400 in VOBU units.

Step #31106 is an effective step for high speed angle switching, andsimply clears the stream buffer 2400. By thus clearing the stream buffer2400 the data for the newly selected angle can be reproduced withoutreproducing the angle data that is still not decoded. In other words,clearing the stream buffer 2400 enables faster response to useroperations.

It is very important that DVD decoder according to the present inventioncan promptly move to the next data reading process and effectivelyperforms the data reading once after the detection of the end of datasuch as interleave unit ILVU and video object unit VOBU for the sake ofseamless reproduction which is one of main targets of the presentinvention.

With reference to FIG. 69, a construction of the stream buffer 2400which can performs the end detection of interleave unit ILVU isdescribed briefly. The stream buffer 2400 comprises a VOB buffer 2402, asystem buffer 2404, a navigation pack extractor 2406, and a data counter2408. The system buffer 2404 temporarily stores the title control dataVTSI(FIG. 16) included in signal St61, and outputs a control informationSt2450 (St63) such as VTS₋₋ PGC.

The VOB buffer 2402 temporarily stores the title VOB data VTSTT₋₋ VOB(FIG. 16), and the stream St67 to the system decoder 2500.

The NV (navigation pack) extractor 2406 receives the VOB data at thesame time with the VOB buffer 2402, and extracts the navigation oack NVtherefrom. The NV extractor 2406 furthermore extracts the VOBU finalpack address COBU₋₋ EA or ILVU final pack address ILVU₋₋ EA which arethe DSI generation information DSI₋₋ GI shown in FIG. 19 to produce apack address information St2452 (St63).

The data counter 2408 receives the VOB data at the same time with theVOB buffer 2402, and counts each of pack data shown in FIG. 19 byte bybyte. Then, the data counter 2408 produces a pack input terminatingsignal St2454 (St63) at the time when the inputting of pack data iscompleted.

Due to its construction shown in FIG. 69, the stream buffer 2400performs the VOBU data transfer as examples at step #31064 of FIG. 64,as follows. The stream buffer 2400 outputs the VOBU data for the NVextractor 2406 and data counter 2408 at the same time when the VOBUbuffer 2400 receives the VOBI data on the top of interleave unit ILVU.As a result, the NV extractor 2406 can extracts the data of ILVU₋₋ EAand Nr₋₋ ILVU₋₋ SA at the same time with the inputting of navigationpack data NV, and outputs thereof as signal St2452 (St63) to the decodesystem controller 2300 (FIG. 26).

The decode system controller 2300 stores the signal St2452 into theILVU₋₋ EA₋₋ reg and NT₋₋ ILVU₋₋ SA₋₋ reg, and then start to counts thenumber of packs based on the pack terminating signal 2452 from the datacounter 2408. Based on the fore mentioned the counted value of packs andILVU₋₋ EA₋₋ reg, the decode system controller 2300 detects the instancewhen the inputting of final pack data of ILVU is completed, or theinputting final byte data of the final pack of the ILVU is completed.Then, the controller 2300 further give a command for the bitstreamreproducer 2000 to move to the position having a sector addressindicated by NT₋₋ ILVU₋₋ SA₋₋ reg. The bitstream producer 2000 moves tothe sector address indicated NT₋₋ ILVU₋₋ SA₋₋ reg, and starts to readthe data. Thus, the detection of final end of ILVU and reading processfor the next ILVU can be performed effectively.

In the above, an example where the multimedia data MBS is reproduced bythe bitstream reproducer 2000 without a buffering process, and isinputted to the stream buffer 2499. However, in the case that the signalprocessor 2008 of the bitstream reproducer 2000 is incorporated with abuffer for error correction process, for example, the controller 2300gives a moving command to reproducer 2000 so that the reproducer 2000moves to the reading position indicated by NT₋₋ ILVU₋₋ SA₋₋ reg aftercompletion of the final pack data of fore mentioned ILVU and clearingthe internal buffer of the reproducer 2000. Thus, the effectivereproduction of ILVU data even when the bitstream reproducer 2000includes a buffer for error correction code (ECC) process.

Furthermore, when the bitstream producer 2000 has a buffer for ECCprocess, the data can be transferred effectively by providing any meanshaving a function equivalent to that of data counter 2408 (FIG. 69). Inother words, the bit stream reproducer 2000 generates the pack inputcompletion signal St62; the decode system controller 2300 give a commandbased on the signal St62 the bitstream reproducer 200 to move to thereading position having sector address designated by NT₋₋ ILVU₋₋ SA₋₋reg. As apparent from the above, the data can be transferred effectivelyeven when the bitstream reproducer 2000 has a function to buffer thedata reproduced from the recording media M.

It is to be noted that the apparatus and method substantially the sameas those described in the above with respect to the interleave unit ILVUcan be used for the detection VOBU end. In other words, by replacing theextraction of ILVU₋₋ EA and NT₋₋ ILVU₋₋ Sa, and the storing of ILVU₋₋EA₋₋ reg and NT₋₋ ILVU₋₋ SA₋₋ reg with the extraction of VOBU₋₋ EA andstoring VOBU₋₋ EA₋₋ reg, the apparatus and method according to thepresent invention, described above, can be used for the detection ofunatend. This is effective for the VOBU data transferring operationsshown at steps #31074, #31082, #31032, and #31102.

Thus, the reading of data such as ILVU and VOBU can be performedeffectively.

Decoding Process in the Stream Buffer

The process for decoding data in the stream buffer 2400 shown as step#31034 in FIG. 57 is described below referring to FIG. 58. This process(step #31034) comprises steps #31110, #31112, #31114, and #31116.

At step #31110 data is transferred in pack units from the stream buffer2400 to the system decoder 2500 (FIG. 26). The procedure then moves tostep #31112.

At step #31112 the pack data is from the stream buffer 2400 to each ofthe buffers, i.e., the video buffer 2600, sub-picture buffer 2700, andaudio buffer 2800.

At step #31112 the Ids of the user-selected audio and sub-picture data.,i.e., the audio ID AUDIO₋₋ ID₋₋ reg and the sub-picture ID SP₋₋ ID₋₋ regstored to the scenario information register shown in FIG. 54, arecompared with the stream ID and sub-stream ID read from the packetheader (FIG. 19), and the matching packets are output to the respectivebuffers. The procedure then moves to step #31114.

The decode timing of the respective decoders (video, sub-picture, andaudio decoders) is controlled in step #31114, i.e., the decodingoperations of the decoders are synchronized, and the procedure moves tostep #31116.

The respective elementary strings are then decoded at step #31116. Thevideo decoder 3801 thus reads and decodes the data from the videobuffer, the sub-picture decoder 3100 reads and decodes the data from thesub-picture buffer, and the audio decoder 3200 reads and decodes thedata from the audio buffer.

This stream buffer data decoding process then terminates when thesedecoding processes are completed.

The decoder synchronization process of step #31114, FIG. 58, isdescribed below with reference to FIG. 59. This processes comprisessteps #31120, #31122, and #31124.

At step #31120 it is determined whether a seamless connection isspecified between the current cell and the preceding cell. If a seamlessconnection, the procedure moves to step #31122, if not, the proceduremoves to step #31124.

A process synchronizing operation for producing seamless connections isexecuted in step #31122, and a process synchronizing operation fornon-seamless connections is executed in step #31124.

To achieve seamless multi-scene reproduction control, it is necessary toseamlessly reproduce the connections between VOB. Except when a VOB,which is normally a single-seam title editing unit, is divided intodiscrete streams, however, there is no contiguity between the SCR andPTS at the connection. The problems relating to reproducing VOB of whichthe SCR and PTS are not contiguous are described below.

Note that the presentation time stamp PTS declaring the videopresentation start time is referenced below as the VPTS, the decodingtime stamp DTS declaring the video decode start time is referenced asVDTS, and the presentation time stamp PTS declaring the audioreproduction, or presentation, start time is referenced as APTS below.

The relationship between the SCR, APTS, and VPTS values and recordingpositions in the VOB are shown in FIG. 47 and described below. Forsimplification this description is limited to the SCR and PTSparameters. The top SCR value is recorded with the PTS to both themiddle audio stream and bottom video stream. If the positions on thehorizontal axis are approximately the same, approximately the same SCRvalue is recorded to each stream.

Tse is the time indicated by the SCR of the last pack in the VOB; Tve isthe time indicated by the VPTS of the last video pack in the VOB; Tae isthe time indicated by the APTS of the last audio pack in the VOB; Tvd isthe video decode buffer delay time; and Tad is the audio decode bufferdelay time.

FIG. 48 is a time line from input of the VOB shown in FIG. 47 to thesystem decoder to output of the last audio and video reproduction data.The horizontal axis shows the passage of time t, and the vertical axisshows the SCR value, which indicates the time transfer should beaccomplished, and the PTS values, which indicate the time reproductionshould be accomplished.

Both audio and video outputs are thus delayed by the respective decodebuffers referenced to the system clock reference SCR, and while theaudio and video data are input substantially simultaneously, the videodata is reproduced at a slight delay after the audio data. This delay iscaused by the difference in the video and audio decode buffer delaytimes.

In addition, when two VOB are connected, there is no contiguity betweenthe SCR and PTS at the connection except when a single-stream VOB issplit into separate streams.

Contiguous; reproduction of VOB #1 and VOB #2 having non-contiguous SCRand PTS parameters is described below referring to FIG. 46.

FIG. 46 also shows the relationship between the SCR, APTS, and VPTSvalues and recording positions in each VOB.

The system clock reference SCR is time information indicating the packtransfer time, and is recorded with each pack; APTS is the audioplayback starting time information recorded with each audio packet; andVPTS is the video playback starting time information recorded with eachvideo packet. The system clock STC is a reference clock for decodersynchronization control.

Tse1 is the time indicated by the SCR of the last pack in VOB #1; Tae1is the time indicated by the last APTS in VOB #1; and Tve1 is the timeindicated by the last VPTS in VOB #1.

Tad is the audio decode buffer delay time; Tvd is the video decodebuffer delay time; and the horizontal axis indicates the passage of timet.

What is important to note here is that synchronizing the audio and videoso that the reproduced audio and video signals are output at the timethe system clock STC equals the APTS and VPTS values in the stream.

To maintain the reference clock for transferring VOB to the systemdecoder, the first system clock reference SCR value in VOB #2 must beset to the STC initializer at precisely time Tse1. However, becausereproduction and output of VOB #1 have not been completed at this timepoint, the audio and video still to be output from VOB #1 after timeTse1 canrot be normally reproduced because the reference clock is lost.

Furthermore, even if the SCR value of the STC initializer is set att theaudio end time Tae1, i.e., later 9 than the system clock reference SCRtime Tse1, the reference clock at which the first pack in VOB #2 shouldbe transferred is lost, and the reference clock for the VOB #1 videooutput to be reproduced after time Tae1 is lost.

The same problem also occurs if the system clock reference SCR is set tothe STC initializer at time Tve1.

When there is a one-to-one correspondence between the VOB reproducedfirst, i.e., the first VOB, and the VOB reproduced thereafter, i.e., thesecond VOB, this problem can be avoided by assuring that the first SCRvalue of the second VOB is contiguous to the last SCR of the first VOB.However, when common data is shared between plural titles, there is amany-to-one relationship between the first VOB and the many VOB that:may be reproduced thereafter.

When contiguously reproducing a second VOB #2 following a first VOB #1,it is therefore necessary to destroy any remaining VOB #1 data in thedecode buffer at time Tse1, and seamless reproduction in which the audioand video are not intermitted is not possible.

A method(s) for seamlessly reproducing VOB of which the SCR and PTS arenot contiguous is described by means of the two embodiments of theinvention below.

Synchronization Controller: Embodiment 1

A first embodiment of the synchronizer 2900 shown in FIG. 26 isdescribed according to the present invention with reference to FIG. 32below. As shown in FIG. 32, the synchronizer 2900 comprises a systemclock STC generator 2902, PTS/DTS extractor 2904, video decodersynchronizer 2906, sub-picture decoder synchronizer 2908, audio decodersynchronizer 2910, and system decoder synchronizer 2912.

The STC generator 2902 generates the system clock for each decoder, andsupplies the synchronization system clock STC to the video decodersynchronizer 2906, sub-picture decoder synchronizer 2908, audio decodersynchronizer 2910, and system decoder synchronizer 2912. The STCgenerator 2902 is described in detail below with reference to FIG. 39.

The PTS/DTS extractor 2904 extracts the presentation time stamp PTS anddecoding time stamp DTS from the synchronization control data St81, andsupplies the PTS and DTS to the decoder synchronizers.

The video decoder synchronizer 2906 generates the video stream decodincgstart signal St89 based on the STC from the STC generator 2902 and thedecoding time stamp DTS for starting video decoding supplied from thePTS/DTS extractor 2904. Mores specifically, the video decodersynchronizer 2906 generates the video stream decoding start signal St89when the STC and DTS match.

The sub-picture decoder synchronizer 2908 generates the sub-picturestream decoding start signal St91 based on the STC from the STCgenerator 2902 and the decoding time stamp DTS for starting sub-picturedecoding supplied from the PTS/DTS extractor 2904. More specifically,the sub-picture decoder synchronizer 2908 generates the sub-picturestream decoding start signal St91 when the STC and DTS match.

The audio decoder synchronizer 2910 generates the audio stream decodingstart signal St93 based on the STC from the STC generator 2902 and thedecoding time stamp DTS for starting audio decoding supplied from thePTS/DTS extractor 2904. More specifically, the audio decodersynchronizer 2910 generates the audio stream decoding start signal St93when the STC and DTS match.

The system decoder synchronizer 2912 outputs the STC from the STCgenerator 2902 as the system clock St79. The system clock St79 is usedto control pack transfers from the stream buffers to the system decoder.In other words, if the STC value exceeds the SCR value in the pack, thepack data is transferred from the stream buffer to the system decoder.

The structure and operation of the STC generator 2902 are described indetail below with reference to FIG. 39. As shown in FIG. 39, the STCgenerator 2902 comprises a system clock STC initializer 32010, STCoffset calculator 32012, STC counter 32014, STC regenerator 32016, STCselection controller 32018, STC selector for video decoder 32020, STCselector for sub-picture decoder 32022, STC selector for audio decoder32024, and STC selector for system decoder 32026.

The STC offset calculator 32012 calculates the offset value STCof usedto update the system clock STC for contiguous reproduction of two VOBswith different initial system clock STC values (SCR).

More specifically, the offset value STC of is calculated by subtractingthe Initial Video Frame Presentation Start Time VOB₋₋ V₋₋ SPTM₋₋ regvalue of the next VOB to be reproduced from the Final Video FramePresentation Termination Time VOB₋₋ V₋₋ EPTM₋₋ reg (see FIG. 39) of theVOB reproduced first.

The STC counter 32014 is a sequential counter that counts from a setvalue synchronized to the system clock, and generates; the referenceclock STCc for each decoder.

The STC regenerator 32016 outputs a reset system clock STCr bysubtracting the offset value STCof calculated by the STC offsetcalculator 32012 from the reference clock STCc supplied from the STCcounter 32014.

The system clock STC initializer 32010 selects and sets the SCR from thefirst pack in the VOB, or the reset system clock STCr output from theSTC regenerator 32016, according to the control signal from the STCselection controller 32018. The value set by the STC initializer 32010is the initial value used by the STC counter 32014.

The STC selector for video decoder 32020 selects either the output STCcfrom the STC counter 32014 or the output STCr from the STC regenerator32016 according to the control signal from the STC selection controller32018, and outputs the selected signal to the video decoder synchronizer2906.

The STC selector for sub-picture decoder 32022 similarly selects eitheroutput STCc or output STCr according to the control signal from the STCselection controller 32018, and outputs the selected signal to thesub-picture decoder synchronizer 2908.

The STC selector for audio decoder 32024 similarly selects either outputSTCc or output STCr according to the control signal from the STCselection controller 32018, and outputs the selected signal to the audiodecoder synchronizer 2910.

The STC selector for system decoder 32026 similarly selects eitheroutput STCc or output STCr according to the control signal from the STCselection controller 32018, and outputs the selected signal to thesystem decoder synchronizer 2912.

The operation of the STC selection controller 32018 during non-seamlessreproduction is described below with reference to FIG. 60. Duringnon-seamless operation (when the SPF₋₋ reg flag₋₋ SML), all STCselectors, i.e., STC selector for video decoder 32020, STC selector forsub-picture decoder 32022, STC selector for audio decoder 32024, and STCselector for system decoder 32026, select and output the reference clockSTCc. More specifically, the STC selectors synchronize decoder operationbased on the reference clock STCc output by the STC counter 32014.

The operation of the STC selection controller 32018 during seamlessreproduction (when the SPF₋₋ reg flag=SML) is also described below withreference to FIG. 40 and FIG. 61.

FIG. 40 also shows the relationship between the SCR, APTS, VDTS, andVPTS values and recording positions in each stream when two VOBs #1 and#2 are connected and seamless reproduced.

The system clock reference SCR is time information indicating the packtransfer time, and is recorded with each pack; APTS is the audioplayback starting time information recorded with each audio packet; VDTSis the video decode start time information recorded with each videopacket; and VPTS is the video playback starting time informationrecorded with each video packet. The system clock STC is a referenceclock for decoder synchronization control.

Tse1 (T1) is the time indicated by the SCR of the last pack in VOB #1;Tae1 (T2) is the time indicated by the last APTS in VOB #1; Tde1 (T3) isthe time indicated by the last VDTS in VOB #1; and Tve1 (T4) is the timeindicated by the last VPTS in VOB #1, i.e., the Final Video FramePresentation Termination Time VOB₋₋ V₋₋ EPTM identified by the last VPTSin VOB #1.

Tad is the audio decode buffer delay time; and Tvd is the video decodebuffer delay time.

Tad is the audio decode buffer delay time; Tdd is the video decodebuffer delay time; and Tve is the sum of the video decode buffer delaytime and the delay until video presentation.

FIG. 61 is a flow chart used to describe the operation of the STCselection controller 32018 shown in FIG. 39 during seamless reproductionoperation.

At step #311220, the STC offset (offset value STCof) is calculated, andthe procedure moves to step #311221.

As described above, the STC offset value STCof is calculated bysubtracting the Initial Video Frame Presentation Start Time VOB₋₋ V₋₋SPTM₋₋ reg value of the next VOB to be reproduced from the Final VideoFrame Presentation Termination Time VOB₋₋ V₋₋ EPTM₋₋ reg (see FIG. 55)of the VOB reproduced first. Thus, the total reproduction time of theVOB reproduced first is calculated as the offset value STCof of the VOBreproduced next.

At step #311221 the calculated STC offset value STCof is applied to theSTC regenerator 32016 to update the system clock STC. The procedure thenmoves to step #311222.

The STC regenerator 32016 updates the system clock STC by subtractingthe output STCof from the STC offset calculator 32012 from the referenceclock STCc output from the STC counter 32014 (STCc-STCof), and outputsthe result as the reset system clock STCr.

At step #311222 the reset system clock STCr is selectively output by theSTC selection controller 32018 to the STC selector for system decoder32026 at time T1 (FIG. 40), i.e., at the time SCR changes from streamVOB #1 to VOB #2. The procedure then moves to step #311223. Thereafterthe reset system clock STCr is applied as the system clock STCreferenced by the system decoder, and the transfer timing of VOB #2 tothe system decoder is determined by the SCR in the pack header of thepack and the STCr.

At step #311223 the reset system clock STCr is selectively output to theSTC selector for audio decoder 32024 at time T2 (FIG. 40), i.e., at thetime APTS changes from stream VOB #1 to VOB #2. The procedure then movesto step #311224. Thereafter the reset system clock STCr is applied asthe system clock STC referenced by the audio decoder, and the VOB #2audio output timing is determined by the APTS in the audio packet andthe STCr. In other words, when the STCr matches the APTS, the audio datacorresponding to that APTS is reproduced.

At step #311224 the reset system clock STCr is selectively output to theSTC selector for video decoder 32020 at time T3 (FIG. 40), i.e., at thetime VDTS changes from stream VOB #1 to VOB #2. The procedure then movesto step #311225. Thereafter the reset system clock STCr is applied asthe system clock STC referenced by the video decoder, and the VOB #2video decode timing is determined by the VDTS in the video packet andthe STCr. In other words, when the STCr matches the VDTS, the video datacorresponding to that VDTS is decoded.

At step #311225 the reset system clock STCr is selectively output to theSTC selector for sub-picture decoder 32022 at time T4 (FIG. 40), i.e.,at the time VPTS changes from stream VOB #1 to VOB #2. The procedurethen moves to step #311225. Thereafter the reset system clock STCr isapplied as the system clock STC referenced by the sub-picture decoder,and the VOB #2 sub-picture presentation timing is determined by thepresentation time stamp PTS in the sub-picture packet and the STCr.

In other words, when the STCr matches the PTS, the sub-picture datecorresponding to that PTS is reproduced. Note that the process fromsub-picture decoding to presentation is accomplished instantaneously. Asa result, the system clock STC value referenced by the sub-picturedecoder changes at the same timing at which the video playback startingtime information VPTS changes from VOB #1 to VOB #2.

At step #311226 the STCr is reset to the STC initializer 32010. The STCinitializer 32010 thus supplies this updated clock to the STC counter32014, which operates using this reset system clock STCr value as theinitial value. The procedure then moves to step #311227.

At step #311227 all of the STC selectors, i.e., STC selector for videodecoder 32020, STC selector for sub-picture decoder 32022, STC selectorfor audio decoder 32024, and STC selector for system decoder 32026,output the reference clock STCc.

Thereafter, the system clock STC referenced by the video decoder,sub-picture decoder, audio decoder, and system decoder is the referenceclock STCc output from the STC counter 32014.

The process from step #311226 to step #311227 must only be accomplishedby the time the system clock reference SCR changes from the VOB #2 SCRto the first SCR in the VOB following VOB #2, i.e., by time T1 at whichthe change to the next OB is accomplished.

Note that the STC switching time T1 can also be obtained by detectingthe change in the Initial Video Frame Presentation Start Time VOB₋₋ V₋₋SPTM or the Final Video Frame Presentation Termination Time VOB₋₋ V₋₋EPTM in the navigation pack NV, and extracting the SCR in the packimmediately before the change. Note that the same VOB₋₋ V₋₋ SPTM andVOB₋₋ V₋₋ EPTM values are recorded to all navigation packs NV in thesame VOB. As a result, when either of these values changes, the VOB hasalso changed, and by monitoring a change in either or these values, itis possible to know that the VOB has changed.

T1 can be obtained by adding the pack transfer time to the SCR value inthe pack immediately before the VOB changed. Note that the pack transfertime is a constant value.

STC switching times T2 and T3 can also be calculated from the APTS,VDTS, and VPTS values extracted immediately before the VOB₋₋ V₋₋ SPTM orVOB₋₋ V₋₋ EPTM value in the navigation pack NV changes.

T2 is calculated by extracting the APTS from the audio packetimmediately before the VOB changes, and adding the audio reproductiontime contained in the audio packet of the corresponding APTS value. Notethat the audio reproduction time contained in the audio packet can becalculated from the audio bit rate and the packet data size.

T3 can be obtained by extracting the VDTS from the video packetcontaining the corresponding VDTS immediately before the VOB changes. T3is thus obtained as the time defined by the VDTS.

T4 is equivalent to the VOB₋₋ V₋₋ EPTM value, which is therefore used.

Synchronization Controller: Embodiment 2

A second embodiment of the synchronizer 2900 shown in FIG. 26 isdescribed according to the present invention with reference to FIG. 41below. As shown in FIG. 41, the synchronizer 2900 comprises a systemclock STC generator 32030, PTS/DTS extractor 32031, synchronizationcontroller 32032, video decoder synchronizer 32033, sub-picture decodersynchronizer 32034, audio decoder synchronizer 32035, and system decodersynchronizer 32036.

The STC generator 32030 generates the system clock for each decoder, andsupplies the synchronization system clock STC to the video decodersynchronizer 32033, sub-picture decoder synchronizer 32034, audiodecoder synchronizer 32035, and system decoder synchronizer 32036. TheSTC generator 32030 is a counter that operates at the system clock. TheSCR from the first pack in the first VOB in the program chain PGC is setas the initial counter value, and is thereafter incremented based on thesystem clock. Note that the initial STC counter value may be reset tothe APTS or VPTS value.

Both the audio and video outputs are reproduced synchronized to therespective output clocks. It is therefore possible for synchronizationto be disrupted by the accumulated error in STC, audio output clock, andvideo output clock precision. When this accumulated error becomes great,the respective decoder buffers may be destroyed (by a data underflow oroverflow state). Therefore, by periodically resetting the system clockSTC to the APTS synchronized to the audio output clock, for example,APTS-STC error accumulation can be prevented, and the audio can bereproduced without interruption. In this case, video synchronization iscontrolled by skipping or freezing video cutput.

This type of synchronization control is defined as Audio Mastersyrchronization control.

On the other hand, by periodically resetting the system clock STC tcothe VPTS synchronized to the video output clock, VPTS-STC erroraccumulation can be prevented, and the video can be seamlesslyreproduced. In this case, audio synchronization is controlled byskipping or pausing audio output.

This type of synchronization control is defined as Video Mastersynchronization control.

In the following description of synchronization control, an ONsynchronization mode refers to STC-referenced synchronization control,either Audio or Video Master. An OFF synchronization mode is whenSTC-referenced synchronization control is not applied. In an OFFsynchronization mode the audio and video decoders sequentially outputthe audio and video at a defined frame frequency based on the respectiveinternal reference clocks without referencing the time stamp values fromthe streams, and no timing control is applied to synchronize the audioand video.

The PTS/DTS extractor 32031 extracts the presentation time stamp PTS anddecoding time stamp DTS from the synchronization control data St81, andsupplies the PTS and DTS to the respective decoder synchronizers.

The synchronization controller 32032 generates the synchronizationcontrol signal specifying an ON or OFF synchronization mode for each ofthe decoder synchronizers. This synchronization controller 32032 isdescribed in detail below with reference to FIG. 42.

If the synchronization control signal from the synchronizationcontroller 32032 specifies an ON synchronization mode, the video decodersynchronizer 32033 generates the video stream decoding start signal St89based on the STC from the STC generator 32030 and the decoding timestamp DTS for starting video decoding supplied from the PTS/DTSextractor 32031. More specifically, the video decoder synchronizer 32033generates the video stream decoding start signal St89 when the STC andDTS match.

If the synchronization control signal from the synchronizationcontroller 32032 specifies an OFF synchronization mode, the videodecoder synchronizer 32033 constantly outputs the video stream decodingstart signal St89. Thus, the video decoder operates independently ofexternal control, and is controlled by internal state information.

If the synchronization control signal from the synchronizationcontroller 32032 specifies an ON synchronization mode, the sub-picturedecoder synchronizer 32034 generates the sub-picture stream decodingstart signal St91 based on the STC from the STC generator 32030 and thedecoding time stamp DTS for starting sub-picture decoding supplied fromthe PTS/DTS extractor 32031. More specifically, the sub-picture decodersynchronizer 32034 generates the sub-picture stream decoding startsignal St91 when the STC and DTS match.

If the synchronization control signal from the synchronizationcontroller 32032 specifies an OFF synchronization mode, the sub-picturedecoder synchronizer 32034 constantly outputs the sub-picture streamdecoding start signal St91. Thus, the sub-picture decoder operatesindependently of external control, and is controlled by internal stateinformation.

If the synchronization control signal from the synchronizationcon-roller 32032 specifies an ON synchronization modes, the audiodecoder synchronizer 32035 generates the audio stream decoding startsignal St93 based on the STC from the STC generator 32030 and thedecoding time stamp DTS for starting audio decoding supplied from thePTS/DTS extractor 32031. More specifically, the audio decodersynchronizer 32035 generates the audio stream decoding start signal St93when the STC and DTS match.

If the synchronization control signal from the synchronizationcontroller 32032 specifies an OFF synchronization mode, the audiodecoder synchronizer 32035 constantly outputs the audio stream decodingstart signal St93. Thus, the audio decoder operates independently ofexternal control, and is controlled by internal state information.

The system decoder synchronizer 32036 outputs the STC from the STCgenerator 32030 as the system clock St79. The system clock St79 is usedto control pack transfers from the stream buffers to the system decoder.In other words, if the STC value matches the SCR value in the pack, thepack data is transferred from the stream buffer to the system decoder.

The structure and operation of the synchronization controller 32032 aredescribed below with reference to FIG. 12 and FIG. 43.

The structure of the synchronization controller 32032 is shown in FIG.42. As shown in the figure, the synchronization controller 32032comprises an SCR change detector 32040, APTS changing time detector32041, VPTS changing time detector 32042, and synchronization modeselector 32043.

The SCR change detector 32040 generates and supplies to thesynchronization mode selector 32043 an ACTIVE SCR change detectionsignal if the SCR value in the pack header in the synchronizationcontrol data St81 changes to 0. By thus setting the SCR to 0 in thefirst pack of the VOB reproduced later when seamlessly connecting andreproducing two VOB, the VOB break point can be easily detected. Notethat the SCR is not set to 0 when an originally contiguous VOB isdivided in two, i.e., when the SCR is contiguous between two VOB.

Note, further, that while a 0 value is described here, any value wherebythe beginning and end of each VOB can be easily determined can be used.

In the case of parental lock control, for example, when a single stream,e.g., VOB #2, is reconnected to one of plural possible scenes, e.g., VOB#1, from the multi-scene period enabling parental lock control, each ofthe VOB in the multi-scene period may have a different reproductiontime, and it is not possible to assign the first SCR value in eachpossible VOB #2 to account for all possible connections. A seamless canbe achieved in such cases, however, by setting the SCR of the first packin VOB #2 to 0.

The APTS changing time detector 32041 compares the APTS in thesynchronization control data St81 when the VOB changes with the STCcounter value supplied from the STC generator 32030 shown in FIG. 41.When the STC counter exceeds the APTS, the APTS changing time detector32041 generates and inputs to the synchronization mode selector 32043 anACTIVE APTS change time detection signal.

Note that the method of detecting the APTS when the VOB changes isdescribed below with reference to FIG. 43.

The VPTS changing time detector 32042 compares the VPTS in thesynchronization control data St81 when the VOB changes with the STCcounter value supplied from the STC generator 32030. When the STCcounter exceeds the VPTS, the VPTS changing time detector 32042generates and inputs to the synchronization mode selector 32043 anACTIVE VPTS change time detection signal.

Note that the method of detecting the VPTS when the VOB changes isdescribed below with reference to FIG. 43.

Based on the SCR change detection signal from the SCR change detector32040, the APTS change time detection signal from the APTS changing timedetector 32041, and the VPTS change time detection signal from the VPTSchanging time detector 32042, the synchronization mode selector 32043generates the synchronization mode selection signals, and outputs to thevideo decoder synchronizer 32033, sub-picture decoder synchronizer32034, audio decoder synchronizer 32035, and system decoder synchronizer32036. The STC update signal STCs is also output to the STC generator32030.

The respective decoder synchronizers control synchronization based onthe system clock STC if an ON synchronization mode is specified. If anOFF synchronization mode is specified, the STC is not used forsynchronization control as described above.

The operation of the synchronization mode selector 32043 is describednext with reference to FIG. 43.

At step #320430 the STC update signal STCs is generated and output tothe STC generator 32030, and the procedure moves to step #320431. If theSTC update signal STCs is ACTIVE, the STC generator 32030 sets a new SCRfrom the synchronization control data St81 as the initial value, andupdates the STC.

At step #320431 the synchronization mode selector 32043 outputs asynchronization mode selection signal specifying an ON synchronizationmode to the decoder synchronizers 32033, 32034, 32035, and 32036. Theprocedure then moves to step #320432.

At step #320432 the procedure moves to step #320433 if the SCR changedetector 32040 detects that the SCR has changed. If an SCR change is notdetected, this step is repeated until an SCR change is detected. As aresult, an ON synchronization mode continues to be output to the decodersynchronizers as long as this step executes.

At step #320433 the synchronization mode selector 32043 outputs asynchronization mode selection signal specifying an OFF synchronizationmode to the decoder synchronizers 32033, 32034, 32035, and 32036. Theprocedure then moves to step #320434. This step thus means that thesynchronization mode is OFF from the time T1 the VOB changed during packtransfer.

If both the APTS changing time detector 32041 and VPTS changing timedetector 32042 detect a changed time at step #320434, control loops backto step #320430, and the synchronization mode is set ON again at step#320431. However, if a changed time is not detected step #320434 repeatsuntil both the APTS and VPTS are detected to change. This step thusmeans that the decoder synchronizers continue operating in an OFFsynchronization mode.

Synchronization control at the start of normal reproduction, i.e., at aVOB start without contiguous reproduction from a preceding VOB, isdescribed next with reference to FIG. 44.

FIG. 44 shows the relationship between the system clock reference SCFIindicating the time a VOB is input to 9 the system decoder data, theaudio playback starting time information APTS, the decoder referenceclock STC, and the video playback starting time VPTS, referenced to timeshown on the horizontal axis with the values expressed in terms of thepresentation start time PST on the vertical axis.

The point at which the first SCR in the VOB is 0 is point A. If thefirst SCR is not 0, e.g., if normal reproduction is resumed from themiddle of a VOB after a special reproduction mode, the control procedureis the same. The times between input and output of the audio data andvideo data, respectively, to and from the system decoder are expressedas DTad and DTvd. Because DTad<DTvd, and data is recorded at the VOBbeginning referenced to the time it is reproduced, only video data ispresent at point C at the VOB start, and the audio data is recorded atpoint D after a delay of DTvd-DTad.

Synchronization is controlled at this point as described below. Videoand audio output is first stopped, the SCR value from the pack at pointA is set to the STC generator 32030, and the STC generator 32030operates an internal counter at the system clock and outputs the systemclock STC. Transfer of the first pack in the VOB to the system decoder2500 starts at the same time. The following packs are transferred at theSCR recorded in the pack header of each pack referenced to the systemclock STC produced by the STC generator 32030.

The first video data is then decoded, and video output starts at point Fwhen the STC output from the STC generator 32030 matches the first VPTSvalue.

Audio output is similarly controlled: the first audio data is decoded,and audio output starts at point E, the moment when the STC output fromthe STC generator 32030 matches the first APTS value.

After reproduction of the start of the VOB thus begins, the audio APTSvalue is periodically set to the STC generator 32030 to controlsynchronization under Audio Master or Video Master control.

The method of synchronizing seamless reproduction of two VOB isdescribed next. The detection method of the SCR change detector 32040,APTS changing time detector 32041, and VPTS changing time detector 32042in FIG. 42 is particularly described with reference to FIG. 45.

FIG. 45 shows the relationship between the recording positions andvalues of SCR, APTS, and VPTS when VOB #1 and VOB #2 are seamlesslyreproduced. Why the synchronization mode of the decoder synchronizersmust be switched ON and OFF to achieve seamless reproduction isdescribed first.

Point G is the time at which the pack being transferred changes from VOB#1 to VOB #2, H is the time the audio output changes, and I is the timethe video output changes. Because the audio output and video output thuschange at different times, synchronization control cannot be achievedusing a single system clock STC. It is therefore necessary to preventsynchronization control using the STC during the period from when theSCR changes at time G to when both the APTS and VPTS have changed attime I. After both the APTS and VPTS have changed at time I,synchronization control using the STC is again possible and necessary.

The method of detecting the timing at which synchronization control isstopped, i.e., when the synchronization mode is turned OFF, is describednext.

The timing at which the synchronization mode is turned OFF is obtainedfrom the SCR time chart in FIG. 45. VOB #1 is being output to the systemdecoder while the SCR value increases, and SCR becomes 0 only at time G,i.e., when VOB #1 transfer stops and VOB #2 transfer begins. Therefore,by detecting the time at which the SCR value becomes 0, it is known thatVOB #2 is being input to the system decoder, and the synchronizationmode is therefore set OFF at this time Tg.

It is also possible to detect that the SCR is 0 when the value iswritten to the stream buffer. The synchronization mode can also be setOFF when a 0 SCR value is detected written to the stream buffer.

The timing at which synchronization control begins, i.e., when thesynchronization mode is turned from OFF to ON, is described next.

To start synchronization control it is necessary to know when both theaudio and video output have switched from VOB #1 to VOB #2. The momentwhen the audio output changes to VOB #2 can be known by detecting thepoint H at which the APTS value stops increasing. Likewise, the momentwhen the video output changes to VOB #2 can be known by detecting thepoint I at which the VPTS value stops increasing. After both points Hand I have appeared, the synchronization mode is immediately set ON attime Ti.

The timing at which the synchronization mode is set OFF can also bedelayed to a time between time Tg and time Ti, rather then at time Tgwhen an SCR change is detected. By setting the synchronization mode OFFat time Th, i.e., the time at which a change in APTS or VPTS isdetected, between Tg and Ti, the duration of the OFF synchronizationmode can be shortened.

However, when the timing is based on detecting whether both APTS andVPTS values continue increasing, it is clear that both APTS and VPTSvalues must decrease when VOB are connected. In other words, the lastAPTS and VPTS values in a VOB must be greater than the maximum initialAPTS and VPTS values in a VOB.

The maximum initial (DTad and DTvd) APTS and VPTS values are defined asfollows.

The initial APTS and VPTS values are the sums of the video data andaudio data storage times in the video and audio buffers, and the videoreordering time (in MPEG video, the picture decode order andpresentation order are not necessarily the same, and presentation isdelayed a maximum one picture from the decoder). Therefore, the sum ofthe time required for the video buffer and audio buffer to fill, and thepresentation delay (1 frame period) from video reordering, determinesthe maximum initial values for APTS and VPTS.

As a result, the last APTS and VPTS values in a VOB are always assignedto exceed these maximum initial values when the VOB are produced.

While it is possible to control the timing at which the synchronizationmode is turned ON following VOB connection by detecting whether bothAPTS and VPTS values continue increasing, it is also possible to achievethe same synchronization control by detecting the time at which the APTSvalue drops below an APTS threshold value, and the VPTS value dropsbelow an VPTS threshold value.

These APTS and VPTS threshold values can be calculated by using valuesequal to the maximum initial APTS and VPTS values of the VOB as thethreshold values, and calculating them as described above.

By applying ON/OFF synchronization mode control as described above,seamless reproduction that does not disturb the playback condition canbe achieved in VOB connections.

Note that various methods can be used in the reproduction apparatus foraudio and video synchronization control in the second embodimentdescribed above. The most common of these methods (1) is to reset thesystem clock STC to the APTS value every few seconds, determine whetherthe VPTS value is first or slow referenced to the system clock STC, andfreeze or skip video output as necessary. This is the so-called AudioMaster method described above.

Alternatively, it is also possible (2) to reset the system clock STC tothe VPTS value every few seconds, determine whether the APTS value isfast or slow referenced to the system clock STC, and freeze or skipaudio output as necessary. This is the so-called Video Master methoddescribed above.

Another method (3) is to directly compare the APTS and VPTS values, anduse either the APTS or VPTS value for reference.

Regardless; of which method is used for ON/OFF synchronization modecontrol, however, the same effect can be achieved.

As described above, two methods are used for audio-videosynchrornization according to the present embodiment, Audio Master andVideo Master synchronization control. For Audio Faster synchronizationcontrol the system clock STC is periodically reset to the APTS value,whether the VPTS value is earlier or later is determined referenced tothe re(set system clock STC, and the video presentation is frozen orskipped as necessary for synchronization. For Video Mastersynchronization control the system clock STC is periodically reset tothe VPTS value, whether the APTS value is earlier or later is determinedreferenced to the reset system clock STC, and the audio presentation ispaused or skipped as necessary for synchronization. It is also possibleto directly compare the APTS and VPTS values, and controlsynchronization referenced to either the APTS or VPTS value. Regardlessof which method is used for AV synchronization control, however, thesame effects can be obtained.

Furthermore, while the above embodiments have been described using aninitial VOB SCR value of 0, a value other than 0 can be used and thesame control achieved by adding the first SCR value as an offset valueto the APTS and VPTS values.

It is also possible in the second embodiment above to read the SECdiscontinuity flag STCDCF₋₋ reg, which specifies whether the next cellreproduced needs the STC to be reset. If the register reads STC₋₋NRESET, the synchronization mode is constantly ON; if STC₋₋ RESET isstored, ON/OFF synchronization mode control can be applied.

It is thus possible to decode the data transferred to the stream buffer2400 while synchronizing the operation of the various decoders.

It is therefore possible by means of the present invention thusdescribed to maintain synchronization between the audio and video data,and seamlessly connect and reproduce two VOB during reproduction from amulti-scene period even when there is no continuity between the systemclock reference SCR and presentation time stamp PTS values used forsynchronization control of the VOB to be contiguously reproduced.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications are apparent to those skilled in the art. Such changes andmodifications are to be understood as included within the scope of thepresent invention as defined by the appended claims unless they departtherefrom.

What is claimed is:
 1. A data stream reproduction apparatus forreproducing data streams, including a plurality of data units, afterstoring the data streams in a buffer, the data units being respectivelyassociated with first time codes for indicating transfer timings atwhich the respective data units are input to the buffer, at least onedata unit being associated with a second time code for indicating apresentation timing at which the at least one data unit is reproduced,the apparatus comprising:a decoder, which includes the buffer, forstoring the data streams input thereto and then decoding the stored datastreams with reference to a reference clock, so as to reproduce thestored data streams based on the second time code in such a manner thatthe at least one data unit with the second time code is reproduced atthe presentation timing; a data stream supplying means for supplying thedata streams to the buffer with reference to the reference clock so asto input the data units at the transfer timings based on the first timecodes, respectively, and a controller for supplying, the reference clockto the decoder and the data stream supplying means, wherein thecontroller comprises:a system clock generator for generating a firstclock and a second clock different from the first clock; and a systemclock selector for selectively outputting the first and second clocks insuch a manner that, during a first period, one of the first and secondclocks is supplied as the reference clock both to the data streamsupplying means and the decoder and, during a second period, one of thefirst and second clocks is supplied to the data stream supplying meanswhile the other of the first and second clocks is supplied to thedecoder.
 2. A data stream reproduction apparatus according to claim 1,wherein the data streams include a first data stream and a second datastream following the first data stream, the first and second datastreams to be reproduced contiguously, andwherein the first periodterminates after a last data unit of the first data stream is suppliedto the buffer of the decoder, while the second period follows the firstperiod and terminates after the last data unit of the first data systemis reproduced.
 3. An optical disk for use with a data streamreproduction apparatus, the data stream reproduction apparatus is forreproducing data streams, including a plurality of data units, afterstoring the data streams in a buffer, the data units being respectivelyassociated with first time codes for indicating transfer timings atwhich the respective data units are input to the buffer, at least onedata unit being associated with a second time code for indicating apresentation timing at which the at least one data unit isreproduced,the apparatus including:a decoder, which includes the buffer,for storing the data streams input thereto and then decoding the storeddata streams with reference to a reference clock, so as to reproduce thestored data streams based on the second time code in such a manner thatthe at least one data unit with the second time code is reproduced atthe presentation timing; a data stream supplying means for supplying thedata streams to the buffer with reference to the reference clock so asto input the data units at the transfer timings based on the first timecodes, respectively, and a controller for supplying the reference clockto the decoder and the data stream supplying means, wherein thecontroller comprises:a system lock generator for generating a firstclock and a second clock different from the first clock; and a systemclock selector for selectively outputting the first and second clocks insuch a manner that, during a first period, one of the first and secondclocks is supplied as the reference clock both to the data streamsupplying means and the decoder and, during a second period, one of thefirst and second clocks is supplied to the data stream supplying meanswhile the other of the first and second clocks is supplied to thedecoder; the optical disk comprising:a data region for storing the datastreams including first and second data streams; and a managementinformation region for storing connection information which is utilizedduring data stream reproduction and indicates that the first data streamis followed by the second data stream, wherein the connectioninformation includes system clock selection information for use duringdata stream reproduction so that the first data stream is supplied tothe buffer and then decoded with reference to one of the first andsecond clocks while the second data stream is supplied to the buffer andthen decoded with reference to the other of the first and second clocks.4. An optical disk according to claim 3, wherein the first and seconddata streams are to be reproduced contiguously, andwherein the firstperiod terminates after a last data unit of the first data stream issupplied to the buffer of the decoder, while the second period followsthe first period and terminates after the last data unit of the firstdata stream is reproduced.
 5. A data stream reproduction method forreproducing data streams, including a plurality of data units, afterstoring the data streams in a buffer, the data units being respectivelyassociated with first time codes for indicating transfer timings atwhich the respective data units are input to the buffer, at least onedata unit being associated with a second time code for indicating apresentation timing at which the at least one data unit is reproduced,the method comprising:storing the data streams in a decoder, whichincludes the buffer, and then decoding the stored data streams withreference to a reference clock, so as to reproduce the stored datastreams based on the second time code in such a manner that the at leastone data unit with the second time code is reproduced at thepresentation timing; supplying the data streams to the buffer via a datastream supplying means with reference to the reference clock so as toinput the data units at the transfer timings based on the first timecodes, respectively, and supplying the reference clock to the decoderand the data stream supplying means, wherein supplying the referenceclock includes:generating a first clock and a second clock differentfrom the first clock; and selectively outputting the first and secondclocks in such a manner that, during a first period, one of the firstand second clocks is supplied as the reference clock both to the datastream supplying means and the decoder and, during a second period, oneof the first and second clocks is supplied to the data stream supplyingmeans while the other of the first and second clocks is supplied to thedecoder.
 6. A data stream reproduction method according to claim 5,wherein the data streams include a first data stream and a second datastream following the first data stream, the first and second datastreams to be reproduced contiguously, andwherein the first periodterminates after a last data unit of the first data stream is suppliedto the buffer of the decoder, while the second period follows the firstperiod and terminates after the last data unit of the first data systemis reproduced.